1 files changed, 594 insertions, 513 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 6afff725a8c9..89c20d9d50bf 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -49,7 +49,6 @@
 
 #include <asm/uaccess.h>
 
-#include <linux/config.h>
 #include <linux/errno.h>
 #include <linux/time.h>
 #include <linux/proc_fs.h>
@@ -74,6 +73,16 @@
 #include <linux/poll.h>
 #include "internal.h"
 
+/* NOTE:
+ *      Implementing inode permission operations in /proc is almost
+ *      certainly an error.  Permission checks need to happen during
+ *      each system call not at open time.  The reason is that most of
+ *      what we wish to check for permissions in /proc varies at runtime.
+ *
+ *      The classic example of a problem is opening file descriptors
+ *      in /proc for a task before it execs a suid executable.
+ */
+
 /*
  * For hysterical raisins we keep the same inumbers as in the old procfs.
  * Feel free to change the macro below - just keep the range distinct from
@@ -121,6 +130,8 @@ enum pid_directory_inos {
         PROC_TGID_ATTR_PREV,
         PROC_TGID_ATTR_EXEC,
         PROC_TGID_ATTR_FSCREATE,
+        PROC_TGID_ATTR_KEYCREATE,
+        PROC_TGID_ATTR_SOCKCREATE,
 #endif
 #ifdef CONFIG_AUDITSYSCALL
         PROC_TGID_LOGINUID,
@@ -162,6 +173,8 @@ enum pid_directory_inos {
         PROC_TID_ATTR_PREV,
         PROC_TID_ATTR_EXEC,
         PROC_TID_ATTR_FSCREATE,
+        PROC_TID_ATTR_KEYCREATE,
+        PROC_TID_ATTR_SOCKCREATE,
 #endif
 #ifdef CONFIG_AUDITSYSCALL
         PROC_TID_LOGINUID,
@@ -173,6 +186,9 @@ enum pid_directory_inos {
         PROC_TID_FD_DIR = 0x8000,       /* 0x8000-0xffff */
 };
 
+/* Worst case buffer size needed for holding an integer. */
+#define PROC_NUMBUF 10
+
 struct pid_entry {
         int type;
         int len;
@@ -275,6 +291,8 @@ static struct pid_entry tgid_attr_stuff[] = {
         E(PROC_TGID_ATTR_PREV,     "prev",     S_IFREG|S_IRUGO),
         E(PROC_TGID_ATTR_EXEC,     "exec",     S_IFREG|S_IRUGO|S_IWUGO),
         E(PROC_TGID_ATTR_FSCREATE, "fscreate", S_IFREG|S_IRUGO|S_IWUGO),
+        E(PROC_TGID_ATTR_KEYCREATE, "keycreate", S_IFREG|S_IRUGO|S_IWUGO),
+        E(PROC_TGID_ATTR_SOCKCREATE, "sockcreate", S_IFREG|S_IRUGO|S_IWUGO),
         {0,0,NULL,0}
 };
 static struct pid_entry tid_attr_stuff[] = {
@@ -282,6 +300,8 @@ static struct pid_entry tid_attr_stuff[] = {
         E(PROC_TID_ATTR_PREV,      "prev",     S_IFREG|S_IRUGO),
         E(PROC_TID_ATTR_EXEC,      "exec",     S_IFREG|S_IRUGO|S_IWUGO),
         E(PROC_TID_ATTR_FSCREATE,  "fscreate", S_IFREG|S_IRUGO|S_IWUGO),
+        E(PROC_TID_ATTR_KEYCREATE, "keycreate", S_IFREG|S_IRUGO|S_IWUGO),
+        E(PROC_TID_ATTR_SOCKCREATE, "sockcreate", S_IFREG|S_IRUGO|S_IWUGO),
         {0,0,NULL,0}
 };
 #endif
@@ -290,12 +310,15 @@ static struct pid_entry tid_attr_stuff[] = {
 
 static int proc_fd_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
 {
-        struct task_struct *task = proc_task(inode);
-        struct files_struct *files;
+        struct task_struct *task = get_proc_task(inode);
+        struct files_struct *files = NULL;
         struct file *file;
-        int fd = proc_type(inode) - PROC_TID_FD_DIR;
+        int fd = proc_fd(inode);
 
-        files = get_files_struct(task);
+        if (task) {
+                files = get_files_struct(task);
+                put_task_struct(task);
+        }
         if (files) {
                 /*
                  * We are not taking a ref to the file structure, so we must
@@ -327,29 +350,33 @@ static struct fs_struct *get_fs_struct(struct task_struct *task)
         return fs;
 }
 
-static int proc_cwd_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
+static int get_nr_threads(struct task_struct *tsk)
 {
-        struct fs_struct *fs = get_fs_struct(proc_task(inode));
-        int result = -ENOENT;
-        if (fs) {
-                read_lock(&fs->lock);
-                *mnt = mntget(fs->pwdmnt);
-                *dentry = dget(fs->pwd);
-                read_unlock(&fs->lock);
-                result = 0;
-                put_fs_struct(fs);
+        /* Must be called with the rcu_read_lock held */
+        unsigned long flags;
+        int count = 0;
+
+        if (lock_task_sighand(tsk, &flags)) {
+                count = atomic_read(&tsk->signal->count);
+                unlock_task_sighand(tsk, &flags);
         }
-        return result;
+        return count;
 }
 
-static int proc_root_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
+static int proc_cwd_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
 {
-        struct fs_struct *fs = get_fs_struct(proc_task(inode));
+        struct task_struct *task = get_proc_task(inode);
+        struct fs_struct *fs = NULL;
         int result = -ENOENT;
+
+        if (task) {
+                fs = get_fs_struct(task);
+                put_task_struct(task);
+        }
         if (fs) {
                 read_lock(&fs->lock);
-                *mnt = mntget(fs->rootmnt);
-                *dentry = dget(fs->root);
+                *mnt = mntget(fs->pwdmnt);
+                *dentry = dget(fs->pwd);
                 read_unlock(&fs->lock);
                 result = 0;
                 put_fs_struct(fs);
@@ -357,42 +384,16 @@ static int proc_root_link(struct inode *inode, struct dentry **dentry, struct vf
         return result;
 }
 
-
-/* Same as proc_root_link, but this addionally tries to get fs from other
- * threads in the group */
-static int proc_task_root_link(struct inode *inode, struct dentry **dentry,
-                                struct vfsmount **mnt)
+static int proc_root_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
 {
-        struct fs_struct *fs;
+        struct task_struct *task = get_proc_task(inode);
+        struct fs_struct *fs = NULL;
         int result = -ENOENT;
-        struct task_struct *leader = proc_task(inode);
 
-        task_lock(leader);
-        fs = leader->fs;
-        if (fs) {
-                atomic_inc(&fs->count);
-                task_unlock(leader);
-        } else {
-                /* Try to get fs from other threads */
-                task_unlock(leader);
-                read_lock(&tasklist_lock);
-                if (pid_alive(leader)) {
-                        struct task_struct *task = leader;
-
-                        while ((task = next_thread(task)) != leader) {
-                                task_lock(task);
-                                fs = task->fs;
-                                if (fs) {
-                                        atomic_inc(&fs->count);
-                                        task_unlock(task);
-                                        break;
-                                }
-                                task_unlock(task);
-                        }
-                }
-                read_unlock(&tasklist_lock);
+        if (task) {
+                fs = get_fs_struct(task);
+                put_task_struct(task);
         }
-
         if (fs) {
                 read_lock(&fs->lock);
                 *mnt = mntget(fs->rootmnt);
@@ -404,7 +405,6 @@ static int proc_task_root_link(struct inode *inode, struct dentry **dentry,
         return result;
 }
 
-
 #define MAY_PTRACE(task) \
         (task == current || \
         (task->parent == current && \
@@ -535,141 +535,42 @@ static int proc_oom_score(struct task_struct *task, char *buffer)
 /************************************************************************/
 
 /* permission checks */
-
-/* If the process being read is separated by chroot from the reading process,
- * don't let the reader access the threads.
- *
- * note: this does dput(root) and mntput(vfsmnt) on exit.
- */
-static int proc_check_chroot(struct dentry *root, struct vfsmount *vfsmnt)
+static int proc_fd_access_allowed(struct inode *inode)
 {
-        struct dentry *de, *base;
-        struct vfsmount *our_vfsmnt, *mnt;
-        int res = 0;
-
-        read_lock(&current->fs->lock);
-        our_vfsmnt = mntget(current->fs->rootmnt);
-        base = dget(current->fs->root);
-        read_unlock(&current->fs->lock);
-
-        spin_lock(&vfsmount_lock);
-        de = root;
-        mnt = vfsmnt;
-
-        while (mnt != our_vfsmnt) {
-                if (mnt == mnt->mnt_parent)
-                        goto out;
-                de = mnt->mnt_mountpoint;
-                mnt = mnt->mnt_parent;
-        }
-
-        if (!is_subdir(de, base))
-                goto out;
-        spin_unlock(&vfsmount_lock);
-
-exit:
-        dput(base);
-        mntput(our_vfsmnt);
-        dput(root);
-        mntput(vfsmnt);
-        return res;
-out:
-        spin_unlock(&vfsmount_lock);
-        res = -EACCES;
-        goto exit;
-}
-
-static int proc_check_root(struct inode *inode)
-{
-        struct dentry *root;
-        struct vfsmount *vfsmnt;
-
-        if (proc_root_link(inode, &root, &vfsmnt)) /* Ewww... */
-                return -ENOENT;
-        return proc_check_chroot(root, vfsmnt);
-}
-
-static int proc_permission(struct inode *inode, int mask, struct nameidata *nd)
-{
-        if (generic_permission(inode, mask, NULL) != 0)
-                return -EACCES;
-        return proc_check_root(inode);
-}
-
-static int proc_task_permission(struct inode *inode, int mask, struct nameidata *nd)
-{
-        struct dentry *root;
-        struct vfsmount *vfsmnt;
-
-        if (generic_permission(inode, mask, NULL) != 0)
-                return -EACCES;
-
-        if (proc_task_root_link(inode, &root, &vfsmnt))
-                return -ENOENT;
-
-        return proc_check_chroot(root, vfsmnt);
-}
-
-extern struct seq_operations proc_pid_maps_op;
-static int maps_open(struct inode *inode, struct file *file)
-{
-        struct task_struct *task = proc_task(inode);
-        int ret = seq_open(file, &proc_pid_maps_op);
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                m->private = task;
+        struct task_struct *task;
+        int allowed = 0;
+        /* Allow access to a task's file descriptors if it is us or we
+         * may use ptrace attach to the process and find out that
+         * information.
+         */
+        task = get_proc_task(inode);
+        if (task) {
+                allowed = ptrace_may_attach(task);
+                put_task_struct(task);
         }
-        return ret;
+        return allowed;
 }
 
-static struct file_operations proc_maps_operations = {
-        .open           = maps_open,
-        .read           = seq_read,
-        .llseek         = seq_lseek,
-        .release        = seq_release,
-};
-
-#ifdef CONFIG_NUMA
-extern struct seq_operations proc_pid_numa_maps_op;
-static int numa_maps_open(struct inode *inode, struct file *file)
+static int proc_setattr(struct dentry *dentry, struct iattr *attr)
 {
-        struct task_struct *task = proc_task(inode);
-        int ret = seq_open(file, &proc_pid_numa_maps_op);
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                m->private = task;
-        }
-        return ret;
-}
+        int error;
+        struct inode *inode = dentry->d_inode;
 
-static struct file_operations proc_numa_maps_operations = {
-        .open           = numa_maps_open,
-        .read           = seq_read,
-        .llseek         = seq_lseek,
-        .release        = seq_release,
-};
-#endif
+        if (attr->ia_valid & ATTR_MODE)
+                return -EPERM;
 
-#ifdef CONFIG_MMU
-extern struct seq_operations proc_pid_smaps_op;
-static int smaps_open(struct inode *inode, struct file *file)
-{
-        struct task_struct *task = proc_task(inode);
-        int ret = seq_open(file, &proc_pid_smaps_op);
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                m->private = task;
+        error = inode_change_ok(inode, attr);
+        if (!error) {
+                error = security_inode_setattr(dentry, attr);
+                if (!error)
+                        error = inode_setattr(inode, attr);
         }
-        return ret;
+        return error;
 }
 
-static struct file_operations proc_smaps_operations = {
-        .open           = smaps_open,
-        .read           = seq_read,
-        .llseek         = seq_lseek,
-        .release        = seq_release,
+static struct inode_operations proc_def_inode_operations = {
+        .setattr        = proc_setattr,
 };
-#endif
 
 extern struct seq_operations mounts_op;
 struct proc_mounts {
@@ -679,16 +580,19 @@ struct proc_mounts {
 
 static int mounts_open(struct inode *inode, struct file *file)
 {
-        struct task_struct *task = proc_task(inode);
-        struct namespace *namespace;
+        struct task_struct *task = get_proc_task(inode);
+        struct namespace *namespace = NULL;
         struct proc_mounts *p;
         int ret = -EINVAL;
 
-        task_lock(task);
-        namespace = task->namespace;
-        if (namespace)
-                get_namespace(namespace);
-        task_unlock(task);
+        if (task) {
+                task_lock(task);
+                namespace = task->namespace;
+                if (namespace)
+                        get_namespace(namespace);
+                task_unlock(task);
+                put_task_struct(task);
+        }
 
         if (namespace) {
                 ret = -ENOMEM;
@@ -745,17 +649,21 @@ static struct file_operations proc_mounts_operations = {
 extern struct seq_operations mountstats_op;
 static int mountstats_open(struct inode *inode, struct file *file)
 {
-        struct task_struct *task = proc_task(inode);
         int ret = seq_open(file, &mountstats_op);
 
         if (!ret) {
                 struct seq_file *m = file->private_data;
-                struct namespace *namespace;
-                task_lock(task);
-                namespace = task->namespace;
-                if (namespace)
-                        get_namespace(namespace);
-                task_unlock(task);
+                struct namespace *namespace = NULL;
+                struct task_struct *task = get_proc_task(inode);
+
+                if (task) {
+                        task_lock(task);
+                        namespace = task->namespace;
+                        if (namespace)
+                                get_namespace(namespace);
+                        task_unlock(task);
+                        put_task_struct(task);
+                }
 
                 if (namespace)
                         m->private = namespace;
@@ -782,18 +690,27 @@ static ssize_t proc_info_read(struct file * file, char __user * buf,
         struct inode * inode = file->f_dentry->d_inode;
         unsigned long page;
         ssize_t length;
-        struct task_struct *task = proc_task(inode);
+        struct task_struct *task = get_proc_task(inode);
+
+        length = -ESRCH;
+        if (!task)
+                goto out_no_task;
 
         if (count > PROC_BLOCK_SIZE)
                 count = PROC_BLOCK_SIZE;
+
+        length = -ENOMEM;
         if (!(page = __get_free_page(GFP_KERNEL)))
-                return -ENOMEM;
+                goto out;
 
         length = PROC_I(inode)->op.proc_read(task, (char*)page);
 
         if (length >= 0)
                 length = simple_read_from_buffer(buf, count, ppos, (char *)page, length);
         free_page(page);
+out:
+        put_task_struct(task);
+out_no_task:
         return length;
 }
 
@@ -810,12 +727,15 @@ static int mem_open(struct inode* inode, struct file* file)
 static ssize_t mem_read(struct file * file, char __user * buf,
                         size_t count, loff_t *ppos)
 {
-        struct task_struct *task = proc_task(file->f_dentry->d_inode);
+        struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
         char *page;
         unsigned long src = *ppos;
         int ret = -ESRCH;
         struct mm_struct *mm;
 
+        if (!task)
+                goto out_no_task;
+
         if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
                 goto out;
 
@@ -865,6 +785,8 @@ out_put:
 out_free:
         free_page((unsigned long) page);
 out:
+        put_task_struct(task);
+out_no_task:
         return ret;
 }
 
@@ -875,18 +797,24 @@ out:
 static ssize_t mem_write(struct file * file, const char * buf,
                          size_t count, loff_t *ppos)
 {
-        int copied = 0;
+        int copied;
         char *page;
-        struct task_struct *task = proc_task(file->f_dentry->d_inode);
+        struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
         unsigned long dst = *ppos;
 
+        copied = -ESRCH;
+        if (!task)
+                goto out_no_task;
+
         if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
-                return -ESRCH;
+                goto out;
 
+        copied = -ENOMEM;
         page = (char *)__get_free_page(GFP_USER);
         if (!page)
-                return -ENOMEM;
+                goto out;
 
+        copied = 0;
         while (count > 0) {
                 int this_len, retval;
 
@@ -908,6 +836,9 @@ static ssize_t mem_write(struct file * file, const char * buf,
         }
         *ppos = dst;
         free_page((unsigned long) page);
+out:
+        put_task_struct(task);
+out_no_task:
         return copied;
 }
 #endif
@@ -938,13 +869,18 @@ static struct file_operations proc_mem_operations = {
 static ssize_t oom_adjust_read(struct file *file, char __user *buf,
                                 size_t count, loff_t *ppos)
 {
-        struct task_struct *task = proc_task(file->f_dentry->d_inode);
-        char buffer[8];
+        struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
+        char buffer[PROC_NUMBUF];
         size_t len;
-        int oom_adjust = task->oomkilladj;
+        int oom_adjust;
         loff_t __ppos = *ppos;
 
-        len = sprintf(buffer, "%i\n", oom_adjust);
+        if (!task)
+                return -ESRCH;
+        oom_adjust = task->oomkilladj;
+        put_task_struct(task);
+
+        len = snprintf(buffer, sizeof(buffer), "%i\n", oom_adjust);
         if (__ppos >= len)
                 return 0;
         if (count > len-__ppos)
@@ -958,15 +894,15 @@ static ssize_t oom_adjust_read(struct file *file, char __user *buf,
 static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
                                 size_t count, loff_t *ppos)
 {
-        struct task_struct *task = proc_task(file->f_dentry->d_inode);
-        char buffer[8], *end;
+        struct task_struct *task;
+        char buffer[PROC_NUMBUF], *end;
         int oom_adjust;
 
         if (!capable(CAP_SYS_RESOURCE))
                 return -EPERM;
-        memset(buffer, 0, 8);
-        if (count > 6)
-                count = 6;
+        memset(buffer, 0, sizeof(buffer));
+        if (count > sizeof(buffer) - 1)
+                count = sizeof(buffer) - 1;
         if (copy_from_user(buffer, buf, count))
                 return -EFAULT;
         oom_adjust = simple_strtol(buffer, &end, 0);
@@ -974,7 +910,11 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
                 return -EINVAL;
         if (*end == '\n')
                 end++;
+        task = get_proc_task(file->f_dentry->d_inode);
+        if (!task)
+                return -ESRCH;
         task->oomkilladj = oom_adjust;
+        put_task_struct(task);
         if (end - buffer == 0)
                 return -EIO;
         return end - buffer;
@@ -985,22 +925,21 @@ static struct file_operations proc_oom_adjust_operations = {
         .write          = oom_adjust_write,
 };
 
-static struct inode_operations proc_mem_inode_operations = {
-        .permission     = proc_permission,
-};
-
 #ifdef CONFIG_AUDITSYSCALL
 #define TMPBUFLEN 21
 static ssize_t proc_loginuid_read(struct file * file, char __user * buf,
                                   size_t count, loff_t *ppos)
 {
         struct inode * inode = file->f_dentry->d_inode;
-        struct task_struct *task = proc_task(inode);
+        struct task_struct *task = get_proc_task(inode);
         ssize_t length;
         char tmpbuf[TMPBUFLEN];
 
+        if (!task)
+                return -ESRCH;
         length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
                                 audit_get_loginuid(task->audit_context));
+        put_task_struct(task);
         return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
 }
 
@@ -1010,13 +949,12 @@ static ssize_t proc_loginuid_write(struct file * file, const char __user * buf,
         struct inode * inode = file->f_dentry->d_inode;
         char *page, *tmp;
         ssize_t length;
-        struct task_struct *task = proc_task(inode);
         uid_t loginuid;
 
         if (!capable(CAP_AUDIT_CONTROL))
                 return -EPERM;
 
-        if (current != task)
+        if (current != pid_task(proc_pid(inode), PIDTYPE_PID))
                 return -EPERM;
 
         if (count >= PAGE_SIZE)
@@ -1040,7 +978,7 @@ static ssize_t proc_loginuid_write(struct file * file, const char __user * buf,
                 goto out_free_page;
 
         }
-        length = audit_set_loginuid(task, loginuid);
+        length = audit_set_loginuid(current, loginuid);
         if (likely(length == 0))
                 length = count;
 
@@ -1059,13 +997,16 @@ static struct file_operations proc_loginuid_operations = {
 static ssize_t seccomp_read(struct file *file, char __user *buf,
                             size_t count, loff_t *ppos)
 {
-        struct task_struct *tsk = proc_task(file->f_dentry->d_inode);
+        struct task_struct *tsk = get_proc_task(file->f_dentry->d_inode);
         char __buf[20];
         loff_t __ppos = *ppos;
         size_t len;
 
+        if (!tsk)
+                return -ESRCH;
         /* no need to print the trailing zero, so use only len */
         len = sprintf(__buf, "%u\n", tsk->seccomp.mode);
+        put_task_struct(tsk);
         if (__ppos >= len)
                 return 0;
         if (count > len - __ppos)
@@ -1079,29 +1020,43 @@ static ssize_t seccomp_read(struct file *file, char __user *buf,
 static ssize_t seccomp_write(struct file *file, const char __user *buf,
                              size_t count, loff_t *ppos)
 {
-        struct task_struct *tsk = proc_task(file->f_dentry->d_inode);
+        struct task_struct *tsk = get_proc_task(file->f_dentry->d_inode);
         char __buf[20], *end;
         unsigned int seccomp_mode;
+        ssize_t result;
+
+        result = -ESRCH;
+        if (!tsk)
+                goto out_no_task;
 
         /* can set it only once to be even more secure */
+        result = -EPERM;
         if (unlikely(tsk->seccomp.mode))
-                return -EPERM;
+                goto out;
 
+        result = -EFAULT;
         memset(__buf, 0, sizeof(__buf));
         count = min(count, sizeof(__buf) - 1);
         if (copy_from_user(__buf, buf, count))
-                return -EFAULT;
+                goto out;
+
         seccomp_mode = simple_strtoul(__buf, &end, 0);
         if (*end == '\n')
                 end++;
+        result = -EINVAL;
         if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
                 tsk->seccomp.mode = seccomp_mode;
                 set_tsk_thread_flag(tsk, TIF_SECCOMP);
         } else
-                return -EINVAL;
+                goto out;
+        result = -EIO;
         if (unlikely(!(end - __buf)))
-                return -EIO;
-        return end - __buf;
+                goto out;
+        result = end - __buf;
+out:
+        put_task_struct(tsk);
+out_no_task:
+        return result;
 }
 
 static struct file_operations proc_seccomp_operations = {
@@ -1118,10 +1073,8 @@ static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
         /* We don't need a base pointer in the /proc filesystem */
         path_release(nd);
 
-        if (current->fsuid != inode->i_uid && !capable(CAP_DAC_OVERRIDE))
-                goto out;
-        error = proc_check_root(inode);
-        if (error)
+        /* Are we allowed to snoop on the tasks file descriptors? */
+        if (!proc_fd_access_allowed(inode))
                 goto out;
 
         error = PROC_I(inode)->op.proc_get_link(inode, &nd->dentry, &nd->mnt);
@@ -1163,12 +1116,8 @@ static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int b
         struct dentry *de;
         struct vfsmount *mnt = NULL;
 
-        lock_kernel();
-
-        if (current->fsuid != inode->i_uid && !capable(CAP_DAC_OVERRIDE))
-                goto out;
-        error = proc_check_root(inode);
-        if (error)
+        /* Are we allowed to snoop on the tasks file descriptors? */
+        if (!proc_fd_access_allowed(inode))
                 goto out;
 
         error = PROC_I(inode)->op.proc_get_link(inode, &de, &mnt);
@@ -1179,30 +1128,29 @@ static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int b
         dput(de);
         mntput(mnt);
 out:
-        unlock_kernel();
         return error;
 }
 
 static struct inode_operations proc_pid_link_inode_operations = {
         .readlink       = proc_pid_readlink,
-        .follow_link    = proc_pid_follow_link
+        .follow_link    = proc_pid_follow_link,
+        .setattr        = proc_setattr,
 };
 
-#define NUMBUF 10
-
 static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
 {
-        struct inode *inode = filp->f_dentry->d_inode;
-        struct task_struct *p = proc_task(inode);
+        struct dentry *dentry = filp->f_dentry;
+        struct inode *inode = dentry->d_inode;
+        struct task_struct *p = get_proc_task(inode);
         unsigned int fd, tid, ino;
         int retval;
-        char buf[NUMBUF];
+        char buf[PROC_NUMBUF];
         struct files_struct * files;
         struct fdtable *fdt;
 
         retval = -ENOENT;
-        if (!pid_alive(p))
-                goto out;
+        if (!p)
+                goto out_no_task;
         retval = 0;
         tid = p->pid;
 
@@ -1213,7 +1161,7 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
                                 goto out;
                         filp->f_pos++;
                 case 1:
-                        ino = fake_ino(tid, PROC_TID_INO);
+                        ino = parent_ino(dentry);
                         if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0)
                                 goto out;
                         filp->f_pos++;
@@ -1232,7 +1180,7 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
                                         continue;
                                 rcu_read_unlock();
 
-                                j = NUMBUF;
+                                j = PROC_NUMBUF;
                                 i = fd;
                                 do {
                                         j--;
@@ -1241,7 +1189,7 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
                                 } while (i);
 
                                 ino = fake_ino(tid, PROC_TID_FD_DIR + fd);
-                                if (filldir(dirent, buf+j, NUMBUF-j, fd+2, ino, DT_LNK) < 0) {
+                                if (filldir(dirent, buf+j, PROC_NUMBUF-j, fd+2, ino, DT_LNK) < 0) {
                                         rcu_read_lock();
                                         break;
                                 }
@@ -1251,6 +1199,8 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
                         put_files_struct(files);
         }
 out:
+        put_task_struct(p);
+out_no_task:
         return retval;
 }
 
@@ -1262,16 +1212,18 @@ static int proc_pident_readdir(struct file *filp,
         int pid;
         struct dentry *dentry = filp->f_dentry;
         struct inode *inode = dentry->d_inode;
+        struct task_struct *task = get_proc_task(inode);
         struct pid_entry *p;
         ino_t ino;
         int ret;
 
         ret = -ENOENT;
-        if (!pid_alive(proc_task(inode)))
+        if (!task)
                 goto out;
 
         ret = 0;
-        pid = proc_task(inode)->pid;
+        pid = task->pid;
+        put_task_struct(task);
         i = filp->f_pos;
         switch (i) {
         case 0:
@@ -1354,22 +1306,20 @@ static struct inode *proc_pid_make_inode(struct super_block * sb, struct task_st
 
         /* Common stuff */
         ei = PROC_I(inode);
-        ei->task = NULL;
         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
         inode->i_ino = fake_ino(task->pid, ino);
-
-        if (!pid_alive(task))
-                goto out_unlock;
+        inode->i_op = &proc_def_inode_operations;
 
         /*
          * grab the reference to task.
          */
-        get_task_struct(task);
-        ei->task = task;
-        ei->type = ino;
+        ei->pid = get_pid(task->pids[PIDTYPE_PID].pid);
+        if (!ei->pid)
+                goto out_unlock;
+
         inode->i_uid = 0;
         inode->i_gid = 0;
-        if (ino == PROC_TGID_INO || ino == PROC_TID_INO || task_dumpable(task)) {
+        if (task_dumpable(task)) {
                 inode->i_uid = task->euid;
                 inode->i_gid = task->egid;
         }
@@ -1379,7 +1329,6 @@ out:
         return inode;
 
 out_unlock:
-        ei->pde = NULL;
         iput(inode);
         return NULL;
 }
@@ -1393,73 +1342,99 @@ out_unlock:
  *
  * Rewrite the inode's ownerships here because the owning task may have
  * performed a setuid(), etc.
+ *
+ * Before the /proc/pid/status file was created the only way to read
+ * the effective uid of a /process was to stat /proc/pid.  Reading
+ * /proc/pid/status is slow enough that procps and other packages
+ * kept stating /proc/pid.  To keep the rules in /proc simple I have
+ * made this apply to all per process world readable and executable
+ * directories.
  */
 static int pid_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
         struct inode *inode = dentry->d_inode;
-        struct task_struct *task = proc_task(inode);
-        if (pid_alive(task)) {
-                if (proc_type(inode) == PROC_TGID_INO || proc_type(inode) == PROC_TID_INO || task_dumpable(task)) {
+        struct task_struct *task = get_proc_task(inode);
+        if (task) {
+                if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
+                    task_dumpable(task)) {
                         inode->i_uid = task->euid;
                         inode->i_gid = task->egid;
                 } else {
                         inode->i_uid = 0;
                         inode->i_gid = 0;
                 }
+                inode->i_mode &= ~(S_ISUID | S_ISGID);
                 security_task_to_inode(task, inode);
+                put_task_struct(task);
                 return 1;
         }
         d_drop(dentry);
         return 0;
 }
 
+static int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+        struct inode *inode = dentry->d_inode;
+        struct task_struct *task;
+        generic_fillattr(inode, stat);
+
+        rcu_read_lock();
+        stat->uid = 0;
+        stat->gid = 0;
+        task = pid_task(proc_pid(inode), PIDTYPE_PID);
+        if (task) {
+                if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
+                    task_dumpable(task)) {
+                        stat->uid = task->euid;
+                        stat->gid = task->egid;
+                }
+        }
+        rcu_read_unlock();
+        return 0;
+}
+
 static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
         struct inode *inode = dentry->d_inode;
-        struct task_struct *task = proc_task(inode);
-        int fd = proc_type(inode) - PROC_TID_FD_DIR;
+        struct task_struct *task = get_proc_task(inode);
+        int fd = proc_fd(inode);
         struct files_struct *files;
 
-        files = get_files_struct(task);
-        if (files) {
-                rcu_read_lock();
-                if (fcheck_files(files, fd)) {
+        if (task) {
+                files = get_files_struct(task);
+                if (files) {
+                        rcu_read_lock();
+                        if (fcheck_files(files, fd)) {
+                                rcu_read_unlock();
+                                put_files_struct(files);
+                                if (task_dumpable(task)) {
+                                        inode->i_uid = task->euid;
+                                        inode->i_gid = task->egid;
+                                } else {
+                                        inode->i_uid = 0;
+                                        inode->i_gid = 0;
+                                }
+                                inode->i_mode &= ~(S_ISUID | S_ISGID);
+                                security_task_to_inode(task, inode);
+                                put_task_struct(task);
+                                return 1;
+                        }
                         rcu_read_unlock();
                         put_files_struct(files);
-                        if (task_dumpable(task)) {
-                                inode->i_uid = task->euid;
-                                inode->i_gid = task->egid;
-                        } else {
-                                inode->i_uid = 0;
-                                inode->i_gid = 0;
-                        }
-                        security_task_to_inode(task, inode);
-                        return 1;
                 }
-                rcu_read_unlock();
-                put_files_struct(files);
+                put_task_struct(task);
         }
         d_drop(dentry);
         return 0;
 }
 
-static void pid_base_iput(struct dentry *dentry, struct inode *inode)
-{
-        struct task_struct *task = proc_task(inode);
-        spin_lock(&task->proc_lock);
-        if (task->proc_dentry == dentry)
-                task->proc_dentry = NULL;
-        spin_unlock(&task->proc_lock);
-        iput(inode);
-}
-
 static int pid_delete_dentry(struct dentry * dentry)
 {
         /* Is the task we represent dead?
          * If so, then don't put the dentry on the lru list,
          * kill it immediately.
          */
-        return !pid_alive(proc_task(dentry->d_inode));
+        return !proc_pid(dentry->d_inode)->tasks[PIDTYPE_PID].first;
 }
 
 static struct dentry_operations tid_fd_dentry_operations =
@@ -1474,13 +1449,6 @@ static struct dentry_operations pid_dentry_operations =
         .d_delete       = pid_delete_dentry,
 };
 
-static struct dentry_operations pid_base_dentry_operations =
-{
-        .d_revalidate   = pid_revalidate,
-        .d_iput         = pid_base_iput,
-        .d_delete       = pid_delete_dentry,
-};
-
 /* Lookups */
 
 static unsigned name_to_int(struct dentry *dentry)
@@ -1508,22 +1476,24 @@ out:
 /* SMP-safe */
 static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry, struct nameidata *nd)
 {
-        struct task_struct *task = proc_task(dir);
+        struct task_struct *task = get_proc_task(dir);
         unsigned fd = name_to_int(dentry);
+        struct dentry *result = ERR_PTR(-ENOENT);
         struct file * file;
         struct files_struct * files;
         struct inode *inode;
         struct proc_inode *ei;
 
+        if (!task)
+                goto out_no_task;
         if (fd == ~0U)
                 goto out;
-        if (!pid_alive(task))
-                goto out;
 
         inode = proc_pid_make_inode(dir->i_sb, task, PROC_TID_FD_DIR+fd);
         if (!inode)
                 goto out;
         ei = PROC_I(inode);
+        ei->fd = fd;
         files = get_files_struct(task);
         if (!files)
                 goto out_unlock;
@@ -1548,19 +1518,25 @@ static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry,
         ei->op.proc_get_link = proc_fd_link;
         dentry->d_op = &tid_fd_dentry_operations;
         d_add(dentry, inode);
-        return NULL;
+        /* Close the race of the process dying before we return the dentry */
+        if (tid_fd_revalidate(dentry, NULL))
+                result = NULL;
+out:
+        put_task_struct(task);
+out_no_task:
+        return result;
 
 out_unlock2:
         spin_unlock(&files->file_lock);
         put_files_struct(files);
 out_unlock:
         iput(inode);
-out:
-        return ERR_PTR(-ENOENT);
+        goto out;
 }
 
 static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldir);
 static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd);
+static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat);
 
 static struct file_operations proc_fd_operations = {
         .read           = generic_read_dir,
@@ -1577,12 +1553,13 @@ static struct file_operations proc_task_operations = {
  */
 static struct inode_operations proc_fd_inode_operations = {
         .lookup         = proc_lookupfd,
-        .permission     = proc_permission,
+        .setattr        = proc_setattr,
 };
 
 static struct inode_operations proc_task_inode_operations = {
         .lookup         = proc_task_lookup,
-        .permission     = proc_task_permission,
+        .getattr        = proc_task_getattr,
+        .setattr        = proc_setattr,
 };
 
 #ifdef CONFIG_SECURITY
@@ -1592,12 +1569,17 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
         struct inode * inode = file->f_dentry->d_inode;
         unsigned long page;
         ssize_t length;
-        struct task_struct *task = proc_task(inode);
+        struct task_struct *task = get_proc_task(inode);
+
+        length = -ESRCH;
+        if (!task)
+                goto out_no_task;
 
         if (count > PAGE_SIZE)
                 count = PAGE_SIZE;
+        length = -ENOMEM;
         if (!(page = __get_free_page(GFP_KERNEL)))
-                return -ENOMEM;
+                goto out;
 
         length = security_getprocattr(task, 
                                       (char*)file->f_dentry->d_name.name, 
@@ -1605,6 +1587,9 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
         if (length >= 0)
                 length = simple_read_from_buffer(buf, count, ppos, (char *)page, length);
         free_page(page);
+out:
+        put_task_struct(task);
+out_no_task:
         return length;
 }
 
@@ -1614,26 +1599,36 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
         struct inode * inode = file->f_dentry->d_inode;
         char *page; 
         ssize_t length; 
-        struct task_struct *task = proc_task(inode); 
+        struct task_struct *task = get_proc_task(inode);
 
+        length = -ESRCH;
+        if (!task)
+                goto out_no_task;
         if (count > PAGE_SIZE) 
                 count = PAGE_SIZE; 
-        if (*ppos != 0) {
-                /* No partial writes. */
-                return -EINVAL;
-        }
+
+        /* No partial writes. */
+        length = -EINVAL;
+        if (*ppos != 0)
+                goto out;
+
+        length = -ENOMEM;
         page = (char*)__get_free_page(GFP_USER); 
         if (!page) 
-                return -ENOMEM;
+                goto out;
+
         length = -EFAULT; 
         if (copy_from_user(page, buf, count)) 
-                goto out;
+                goto out_free;
 
         length = security_setprocattr(task, 
                                       (char*)file->f_dentry->d_name.name, 
                                       (void*)page, count);
-out:
+out_free:
         free_page((unsigned long) page);
+out:
+        put_task_struct(task);
+out_no_task:
         return length;
 } 
 
@@ -1648,24 +1643,22 @@ static struct file_operations proc_tgid_attr_operations;
 static struct inode_operations proc_tgid_attr_inode_operations;
 #endif
 
-static int get_tid_list(int index, unsigned int *tids, struct inode *dir);
-
 /* SMP-safe */
 static struct dentry *proc_pident_lookup(struct inode *dir, 
                                          struct dentry *dentry,
                                          struct pid_entry *ents)
 {
         struct inode *inode;
-        int error;
-        struct task_struct *task = proc_task(dir);
+        struct dentry *error;
+        struct task_struct *task = get_proc_task(dir);
         struct pid_entry *p;
         struct proc_inode *ei;
 
-        error = -ENOENT;
+        error = ERR_PTR(-ENOENT);
         inode = NULL;
 
-        if (!pid_alive(task))
-                goto out;
+        if (!task)
+                goto out_no_task;
 
         for (p = ents; p->name; p++) {
                 if (p->len != dentry->d_name.len)
@@ -1676,7 +1669,7 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
         if (!p->name)
                 goto out;
 
-        error = -EINVAL;
+        error = ERR_PTR(-EINVAL);
         inode = proc_pid_make_inode(dir->i_sb, task, p->type);
         if (!inode)
                 goto out;
@@ -1689,7 +1682,7 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
          */
         switch(p->type) {
                 case PROC_TGID_TASK:
-                        inode->i_nlink = 2 + get_tid_list(2, NULL, dir);
+                        inode->i_nlink = 2;
                         inode->i_op = &proc_task_inode_operations;
                         inode->i_fop = &proc_task_operations;
                         break;
@@ -1759,7 +1752,6 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
 #endif
                 case PROC_TID_MEM:
                 case PROC_TGID_MEM:
-                        inode->i_op = &proc_mem_inode_operations;
                         inode->i_fop = &proc_mem_operations;
                         break;
 #ifdef CONFIG_SECCOMP
@@ -1801,6 +1793,10 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
                 case PROC_TGID_ATTR_EXEC:
                 case PROC_TID_ATTR_FSCREATE:
                 case PROC_TGID_ATTR_FSCREATE:
+                case PROC_TID_ATTR_KEYCREATE:
+                case PROC_TGID_ATTR_KEYCREATE:
+                case PROC_TID_ATTR_SOCKCREATE:
+                case PROC_TGID_ATTR_SOCKCREATE:
                         inode->i_fop = &proc_pid_attr_operations;
                         break;
 #endif
@@ -1842,14 +1838,18 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
                 default:
                         printk("procfs: impossible type (%d)",p->type);
                         iput(inode);
-                        return ERR_PTR(-EINVAL);
+                        error = ERR_PTR(-EINVAL);
+                        goto out;
         }
         dentry->d_op = &pid_dentry_operations;
         d_add(dentry, inode);
-        return NULL;
-
+        /* Close the race of the process dying before we return the dentry */
+        if (pid_revalidate(dentry, NULL))
+                error = NULL;
 out:
-        return ERR_PTR(error);
+        put_task_struct(task);
+out_no_task:
+        return error;
 }
 
 static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd){
@@ -1872,10 +1872,14 @@ static struct file_operations proc_tid_base_operations = {
 
 static struct inode_operations proc_tgid_base_inode_operations = {
         .lookup         = proc_tgid_base_lookup,
+        .getattr        = pid_getattr,
+        .setattr        = proc_setattr,
 };
 
 static struct inode_operations proc_tid_base_inode_operations = {
         .lookup         = proc_tid_base_lookup,
+        .getattr        = pid_getattr,
+        .setattr        = proc_setattr,
 };
 
 #ifdef CONFIG_SECURITY
@@ -1917,10 +1921,14 @@ static struct dentry *proc_tid_attr_lookup(struct inode *dir,
 
 static struct inode_operations proc_tgid_attr_inode_operations = {
         .lookup         = proc_tgid_attr_lookup,
+        .getattr        = pid_getattr,
+        .setattr        = proc_setattr,
 };
 
 static struct inode_operations proc_tid_attr_inode_operations = {
         .lookup         = proc_tid_attr_lookup,
+        .getattr        = pid_getattr,
+        .setattr        = proc_setattr,
 };
 #endif
 
@@ -1930,14 +1938,14 @@ static struct inode_operations proc_tid_attr_inode_operations = {
 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
                               int buflen)
 {
-        char tmp[30];
+        char tmp[PROC_NUMBUF];
         sprintf(tmp, "%d", current->tgid);
         return vfs_readlink(dentry,buffer,buflen,tmp);
 }
 
 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
-        char tmp[30];
+        char tmp[PROC_NUMBUF];
         sprintf(tmp, "%d", current->tgid);
         return ERR_PTR(vfs_follow_link(nd,tmp));
 }       
@@ -1948,67 +1956,80 @@ static struct inode_operations proc_self_inode_operations = {
 };
 
 /**
- * proc_pid_unhash -  Unhash /proc/@pid entry from the dcache.
- * @p: task that should be flushed.
+ * proc_flush_task -  Remove dcache entries for @task from the /proc dcache.
+ *
+ * @task: task that should be flushed.
  *
- * Drops the /proc/@pid dcache entry from the hash chains.
+ * Looks in the dcache for
+ * /proc/@pid
+ * /proc/@tgid/task/@pid
+ * if either directory is present flushes it and all of it'ts children
+ * from the dcache.
  *
- * Dropping /proc/@pid entries and detach_pid must be synchroneous,
- * otherwise e.g. /proc/@pid/exe might point to the wrong executable,
- * if the pid value is immediately reused. This is enforced by
- * - caller must acquire spin_lock(p->proc_lock)
- * - must be called before detach_pid()
- * - proc_pid_lookup acquires proc_lock, and checks that
- *   the target is not dead by looking at the attach count
- *   of PIDTYPE_PID.
+ * It is safe and reasonable to cache /proc entries for a task until
+ * that task exits.  After that they just clog up the dcache with
+ * useless entries, possibly causing useful dcache entries to be
+ * flushed instead.  This routine is proved to flush those useless
+ * dcache entries at process exit time.
+ *
+ * NOTE: This routine is just an optimization so it does not guarantee
+ *       that no dcache entries will exist at process exit time it
+ *       just makes it very unlikely that any will persist.
  */
-
-struct dentry *proc_pid_unhash(struct task_struct *p)
+void proc_flush_task(struct task_struct *task)
 {
-        struct dentry *proc_dentry;
+        struct dentry *dentry, *leader, *dir;
+        char buf[PROC_NUMBUF];
+        struct qstr name;
+
+        name.name = buf;
+        name.len = snprintf(buf, sizeof(buf), "%d", task->pid);
+        dentry = d_hash_and_lookup(proc_mnt->mnt_root, &name);
+        if (dentry) {
+                shrink_dcache_parent(dentry);
+                d_drop(dentry);
+                dput(dentry);
+        }
 
-        proc_dentry = p->proc_dentry;
-        if (proc_dentry != NULL) {
+        if (thread_group_leader(task))
+                goto out;
 
-                spin_lock(&dcache_lock);
-                spin_lock(&proc_dentry->d_lock);
-                if (!d_unhashed(proc_dentry)) {
-                        dget_locked(proc_dentry);
-                        __d_drop(proc_dentry);
-                        spin_unlock(&proc_dentry->d_lock);
-                } else {
-                        spin_unlock(&proc_dentry->d_lock);
-                        proc_dentry = NULL;
-                }
-                spin_unlock(&dcache_lock);
-        }
-        return proc_dentry;
-}
+        name.name = buf;
+        name.len = snprintf(buf, sizeof(buf), "%d", task->tgid);
+        leader = d_hash_and_lookup(proc_mnt->mnt_root, &name);
+        if (!leader)
+                goto out;
 
-/**
- * proc_pid_flush - recover memory used by stale /proc/@pid/x entries
- * @proc_dentry: directoy to prune.
- *
- * Shrink the /proc directory that was used by the just killed thread.
- */
-        
-void proc_pid_flush(struct dentry *proc_dentry)
-{
-        might_sleep();
-        if(proc_dentry != NULL) {
-                shrink_dcache_parent(proc_dentry);
-                dput(proc_dentry);
+        name.name = "task";
+        name.len = strlen(name.name);
+        dir = d_hash_and_lookup(leader, &name);
+        if (!dir)
+                goto out_put_leader;
+
+        name.name = buf;
+        name.len = snprintf(buf, sizeof(buf), "%d", task->pid);
+        dentry = d_hash_and_lookup(dir, &name);
+        if (dentry) {
+                shrink_dcache_parent(dentry);
+                d_drop(dentry);
+                dput(dentry);
         }
+
+        dput(dir);
+out_put_leader:
+        dput(leader);
+out:
+        return;
 }
 
 /* SMP-safe */
 struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd)
 {
+        struct dentry *result = ERR_PTR(-ENOENT);
         struct task_struct *task;
         struct inode *inode;
         struct proc_inode *ei;
         unsigned tgid;
-        int died;
 
         if (dentry->d_name.len == 4 && !memcmp(dentry->d_name.name,"self",4)) {
                 inode = new_inode(dir->i_sb);
@@ -2029,21 +2050,18 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, struct
         if (tgid == ~0U)
                 goto out;
 
-        read_lock(&tasklist_lock);
+        rcu_read_lock();
         task = find_task_by_pid(tgid);
         if (task)
                 get_task_struct(task);
-        read_unlock(&tasklist_lock);
+        rcu_read_unlock();
         if (!task)
                 goto out;
 
         inode = proc_pid_make_inode(dir->i_sb, task, PROC_TGID_INO);
+        if (!inode)
+                goto out_put_task;
 
-
-        if (!inode) {
-                put_task_struct(task);
-                goto out;
-        }
         inode->i_mode = S_IFDIR|S_IRUGO|S_IXUGO;
         inode->i_op = &proc_tgid_base_inode_operations;
         inode->i_fop = &proc_tgid_base_operations;
@@ -2054,45 +2072,40 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, struct
         inode->i_nlink = 4;
 #endif
 
-        dentry->d_op = &pid_base_dentry_operations;
+        dentry->d_op = &pid_dentry_operations;
 
-        died = 0;
         d_add(dentry, inode);
-        spin_lock(&task->proc_lock);
-        task->proc_dentry = dentry;
-        if (!pid_alive(task)) {
-                dentry = proc_pid_unhash(task);
-                died = 1;
-        }
-        spin_unlock(&task->proc_lock);
+        /* Close the race of the process dying before we return the dentry */
+        if (pid_revalidate(dentry, NULL))
+                result = NULL;
 
+out_put_task:
         put_task_struct(task);
-        if (died) {
-                proc_pid_flush(dentry);
-                goto out;
-        }
-        return NULL;
 out:
-        return ERR_PTR(-ENOENT);
+        return result;
 }
 
 /* SMP-safe */
 static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd)
 {
+        struct dentry *result = ERR_PTR(-ENOENT);
         struct task_struct *task;
-        struct task_struct *leader = proc_task(dir);
+        struct task_struct *leader = get_proc_task(dir);
         struct inode *inode;
         unsigned tid;
 
+        if (!leader)
+                goto out_no_task;
+
         tid = name_to_int(dentry);
         if (tid == ~0U)
                 goto out;
 
-        read_lock(&tasklist_lock);
+        rcu_read_lock();
         task = find_task_by_pid(tid);
         if (task)
                 get_task_struct(task);
-        read_unlock(&tasklist_lock);
+        rcu_read_unlock();
         if (!task)
                 goto out;
         if (leader->tgid != task->tgid)
@@ -2113,101 +2126,95 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
         inode->i_nlink = 3;
 #endif
 
-        dentry->d_op = &pid_base_dentry_operations;
+        dentry->d_op = &pid_dentry_operations;
 
         d_add(dentry, inode);
+        /* Close the race of the process dying before we return the dentry */
+        if (pid_revalidate(dentry, NULL))
+                result = NULL;
 
-        put_task_struct(task);
-        return NULL;
 out_drop_task:
         put_task_struct(task);
 out:
-        return ERR_PTR(-ENOENT);
+        put_task_struct(leader);
+out_no_task:
+        return result;
 }
 
-#define PROC_NUMBUF 10
-#define PROC_MAXPIDS 20
-
 /*
- * Get a few tgid's to return for filldir - we need to hold the
- * tasklist lock while doing this, and we must release it before
- * we actually do the filldir itself, so we use a temp buffer..
+ * Find the first tgid to return to user space.
+ *
+ * Usually this is just whatever follows &init_task, but if the users
+ * buffer was too small to hold the full list or there was a seek into
+ * the middle of the directory we have more work to do.
+ *
+ * In the case of a short read we start with find_task_by_pid.
+ *
+ * In the case of a seek we start with &init_task and walk nr
+ * threads past it.
  */
-static int get_tgid_list(int index, unsigned long version, unsigned int *tgids)
-{
-        struct task_struct *p;
-        int nr_tgids = 0;
-
-        index--;
-        read_lock(&tasklist_lock);
-        p = NULL;
-        if (version) {
-                p = find_task_by_pid(version);
-                if (p && !thread_group_leader(p))
-                        p = NULL;
+static struct task_struct *first_tgid(int tgid, unsigned int nr)
+{
+        struct task_struct *pos;
+        rcu_read_lock();
+        if (tgid && nr) {
+                pos = find_task_by_pid(tgid);
+                if (pos && thread_group_leader(pos))
+                        goto found;
         }
+        /* If nr exceeds the number of processes get out quickly */
+        pos = NULL;
+        if (nr && nr >= nr_processes())
+                goto done;
 
-        if (p)
-                index = 0;
-        else
-                p = next_task(&init_task);
-
-        for ( ; p != &init_task; p = next_task(p)) {
-                int tgid = p->pid;
-                if (!pid_alive(p))
-                        continue;
-                if (--index >= 0)
-                        continue;
-                tgids[nr_tgids] = tgid;
-                nr_tgids++;
-                if (nr_tgids >= PROC_MAXPIDS)
-                        break;
+        /* If we haven't found our starting place yet start with
+         * the init_task and walk nr tasks forward.
+         */
+        for (pos = next_task(&init_task); nr > 0; --nr) {
+                pos = next_task(pos);
+                if (pos == &init_task) {
+                        pos = NULL;
+                        goto done;
+                }
         }
-        read_unlock(&tasklist_lock);
-        return nr_tgids;
+found:
+        get_task_struct(pos);
+done:
+        rcu_read_unlock();
+        return pos;
 }
 
 /*
- * Get a few tid's to return for filldir - we need to hold the
- * tasklist lock while doing this, and we must release it before
- * we actually do the filldir itself, so we use a temp buffer..
+ * Find the next task in the task list.
+ * Return NULL if we loop or there is any error.
+ *
+ * The reference to the input task_struct is released.
  */
-static int get_tid_list(int index, unsigned int *tids, struct inode *dir)
-{
-        struct task_struct *leader_task = proc_task(dir);
-        struct task_struct *task = leader_task;
-        int nr_tids = 0;
-
-        index -= 2;
-        read_lock(&tasklist_lock);
-        /*
-         * The starting point task (leader_task) might be an already
-         * unlinked task, which cannot be used to access the task-list
-         * via next_thread().
-         */
-        if (pid_alive(task)) do {
-                int tid = task->pid;
-
-                if (--index >= 0)
-                        continue;
-                if (tids != NULL)
-                        tids[nr_tids] = tid;
-                nr_tids++;
-                if (nr_tids >= PROC_MAXPIDS)
-                        break;
-        } while ((task = next_thread(task)) != leader_task);
-        read_unlock(&tasklist_lock);
-        return nr_tids;
+static struct task_struct *next_tgid(struct task_struct *start)
+{
+        struct task_struct *pos;
+        rcu_read_lock();
+        pos = start;
+        if (pid_alive(start))
+                pos = next_task(start);
+        if (pid_alive(pos) && (pos != &init_task)) {
+                get_task_struct(pos);
+                goto done;
+        }
+        pos = NULL;
+done:
+        rcu_read_unlock();
+        put_task_struct(start);
+        return pos;
 }
 
 /* for the /proc/ directory itself, after non-process stuff has been done */
 int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
 {
-        unsigned int tgid_array[PROC_MAXPIDS];
         char buf[PROC_NUMBUF];
         unsigned int nr = filp->f_pos - FIRST_PROCESS_ENTRY;
-        unsigned int nr_tgids, i;
-        int next_tgid;
+        struct task_struct *task;
+        int tgid;
 
         if (!nr) {
                 ino_t ino = fake_ino(0,PROC_TGID_INO);
@@ -2216,63 +2223,116 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
                 filp->f_pos++;
                 nr++;
         }
+        nr -= 1;
 
         /* f_version caches the tgid value that the last readdir call couldn't
          * return. lseek aka telldir automagically resets f_version to 0.
          */
-        next_tgid = filp->f_version;
+        tgid = filp->f_version;
         filp->f_version = 0;
-        for (;;) {
-                nr_tgids = get_tgid_list(nr, next_tgid, tgid_array);
-                if (!nr_tgids) {
-                        /* no more entries ! */
+        for (task = first_tgid(tgid, nr);
+             task;
+             task = next_tgid(task), filp->f_pos++) {
+                int len;
+                ino_t ino;
+                tgid = task->pid;
+                len = snprintf(buf, sizeof(buf), "%d", tgid);
+                ino = fake_ino(tgid, PROC_TGID_INO);
+                if (filldir(dirent, buf, len, filp->f_pos, ino, DT_DIR) < 0) {
+                        /* returning this tgid failed, save it as the first
+                         * pid for the next readir call */
+                        filp->f_version = tgid;
+                        put_task_struct(task);
                         break;
                 }
-                next_tgid = 0;
+        }
+        return 0;
+}
 
-                /* do not use the last found pid, reserve it for next_tgid */
-                if (nr_tgids == PROC_MAXPIDS) {
-                        nr_tgids--;
-                        next_tgid = tgid_array[nr_tgids];
-                }
+/*
+ * Find the first tid of a thread group to return to user space.
+ *
+ * Usually this is just the thread group leader, but if the users
+ * buffer was too small or there was a seek into the middle of the
+ * directory we have more work todo.
+ *
+ * In the case of a short read we start with find_task_by_pid.
+ *
+ * In the case of a seek we start with the leader and walk nr
+ * threads past it.
+ */
+static struct task_struct *first_tid(struct task_struct *leader,
+                                        int tid, int nr)
+{
+        struct task_struct *pos;
 
-                for (i=0;i<nr_tgids;i++) {
-                        int tgid = tgid_array[i];
-                        ino_t ino = fake_ino(tgid,PROC_TGID_INO);
-                        unsigned long j = PROC_NUMBUF;
+        rcu_read_lock();
+        /* Attempt to start with the pid of a thread */
+        if (tid && (nr > 0)) {
+                pos = find_task_by_pid(tid);
+                if (pos && (pos->group_leader == leader))
+                        goto found;
+        }
 
-                        do
-                                buf[--j] = '0' + (tgid % 10);
-                        while ((tgid /= 10) != 0);
+        /* If nr exceeds the number of threads there is nothing todo */
+        pos = NULL;
+        if (nr && nr >= get_nr_threads(leader))
+                goto out;
 
-                        if (filldir(dirent, buf+j, PROC_NUMBUF-j, filp->f_pos, ino, DT_DIR) < 0) {
-                                /* returning this tgid failed, save it as the first
-                                 * pid for the next readir call */
-                                filp->f_version = tgid_array[i];
-                                goto out;
-                        }
-                        filp->f_pos++;
-                        nr++;
+        /* If we haven't found our starting place yet start
+         * with the leader and walk nr threads forward.
+         */
+        for (pos = leader; nr > 0; --nr) {
+                pos = next_thread(pos);
+                if (pos == leader) {
+                        pos = NULL;
+                        goto out;
                 }
         }
+found:
+        get_task_struct(pos);
 out:
-        return 0;
+        rcu_read_unlock();
+        return pos;
+}
+
+/*
+ * Find the next thread in the thread list.
+ * Return NULL if there is an error or no next thread.
+ *
+ * The reference to the input task_struct is released.
+ */
+static struct task_struct *next_tid(struct task_struct *start)
+{
+        struct task_struct *pos = NULL;
+        rcu_read_lock();
+        if (pid_alive(start)) {
+                pos = next_thread(start);
+                if (thread_group_leader(pos))
+                        pos = NULL;
+                else
+                        get_task_struct(pos);
+        }
+        rcu_read_unlock();
+        put_task_struct(start);
+        return pos;
 }
 
 /* for the /proc/TGID/task/ directories */
 static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldir)
 {
-        unsigned int tid_array[PROC_MAXPIDS];
         char buf[PROC_NUMBUF];
-        unsigned int nr_tids, i;
         struct dentry *dentry = filp->f_dentry;
         struct inode *inode = dentry->d_inode;
+        struct task_struct *leader = get_proc_task(inode);
+        struct task_struct *task;
         int retval = -ENOENT;
         ino_t ino;
+        int tid;
         unsigned long pos = filp->f_pos;  /* avoiding "long long" filp->f_pos */
 
-        if (!pid_alive(proc_task(inode)))
-                goto out;
+        if (!leader)
+                goto out_no_task;
         retval = 0;
 
         switch (pos) {
@@ -2290,24 +2350,45 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
                 /* fall through */
         }
 
-        nr_tids = get_tid_list(pos, tid_array, inode);
-        inode->i_nlink = pos + nr_tids;
-
-        for (i = 0; i < nr_tids; i++) {
-                unsigned long j = PROC_NUMBUF;
-                int tid = tid_array[i];
-
-                ino = fake_ino(tid,PROC_TID_INO);
-
-                do
-                        buf[--j] = '0' + (tid % 10);
-                while ((tid /= 10) != 0);
-
-                if (filldir(dirent, buf+j, PROC_NUMBUF-j, pos, ino, DT_DIR) < 0)
+        /* f_version caches the tgid value that the last readdir call couldn't
+         * return. lseek aka telldir automagically resets f_version to 0.
+         */
+        tid = filp->f_version;
+        filp->f_version = 0;
+        for (task = first_tid(leader, tid, pos - 2);
+             task;
+             task = next_tid(task), pos++) {
+                int len;
+                tid = task->pid;
+                len = snprintf(buf, sizeof(buf), "%d", tid);
+                ino = fake_ino(tid, PROC_TID_INO);
+                if (filldir(dirent, buf, len, pos, ino, DT_DIR < 0)) {
+                        /* returning this tgid failed, save it as the first
+                         * pid for the next readir call */
+                        filp->f_version = tid;
+                        put_task_struct(task);
                         break;
-                pos++;
+                }
         }
 out:
         filp->f_pos = pos;
+        put_task_struct(leader);
+out_no_task:
         return retval;
 }
+
+static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+        struct inode *inode = dentry->d_inode;
+        struct task_struct *p = get_proc_task(inode);
+        generic_fillattr(inode, stat);
+
+        if (p) {
+                rcu_read_lock();
+                stat->nlink += get_nr_threads(p);
+                rcu_read_unlock();
+                put_task_struct(p);
+        }
+
+        return 0;
+}