2 files changed, 152 insertions, 23 deletions

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 3b22bbdee9ec..439ae6886507 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -31,6 +31,7 @@ static void proc_evict_inode(struct inode *inode)
         struct proc_dir_entry *de;
         struct ctl_table_header *head;
         const struct proc_ns_operations *ns_ops;
+        void *ns;
 
         truncate_inode_pages(&inode->i_data, 0);
         clear_inode(inode);
@@ -49,8 +50,9 @@ static void proc_evict_inode(struct inode *inode)
         }
         /* Release any associated namespace */
         ns_ops = PROC_I(inode)->ns_ops;
-        if (ns_ops && ns_ops->put)
-                ns_ops->put(PROC_I(inode)->ns);
+        ns = PROC_I(inode)->ns;
+        if (ns_ops && ns)
+                ns_ops->put(ns);
 }
 
 static struct kmem_cache * proc_inode_cachep;
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 030250c27d70..7a6d8d69cdb8 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -38,6 +38,151 @@ static const struct file_operations ns_file_operations = {
         .llseek         = no_llseek,
 };
 
+static const struct inode_operations ns_inode_operations = {
+        .setattr        = proc_setattr,
+};
+
+static int ns_delete_dentry(const struct dentry *dentry)
+{
+        /* Don't cache namespace inodes when not in use */
+        return 1;
+}
+
+static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+        struct inode *inode = dentry->d_inode;
+        const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
+
+        return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
+                ns_ops->name, inode->i_ino);
+}
+
+const struct dentry_operations ns_dentry_operations =
+{
+        .d_delete       = ns_delete_dentry,
+        .d_dname        = ns_dname,
+};
+
+static struct dentry *proc_ns_get_dentry(struct super_block *sb,
+        struct task_struct *task, const struct proc_ns_operations *ns_ops)
+{
+        struct dentry *dentry, *result;
+        struct inode *inode;
+        struct proc_inode *ei;
+        struct qstr qname = { .name = "", };
+        void *ns;
+
+        ns = ns_ops->get(task);
+        if (!ns)
+                return ERR_PTR(-ENOENT);
+
+        dentry = d_alloc_pseudo(sb, &qname);
+        if (!dentry) {
+                ns_ops->put(ns);
+                return ERR_PTR(-ENOMEM);
+        }
+
+        inode = new_inode(sb);
+        if (!inode) {
+                dput(dentry);
+                ns_ops->put(ns);
+                return ERR_PTR(-ENOMEM);
+        }
+
+        ei = PROC_I(inode);
+        inode->i_ino = get_next_ino();
+        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+        inode->i_op = &ns_inode_operations;
+        inode->i_mode = S_IFREG | S_IRUGO;
+        inode->i_fop = &ns_file_operations;
+        ei->ns_ops = ns_ops;
+        ei->ns = ns;
+
+        d_set_d_op(dentry, &ns_dentry_operations);
+        result = d_instantiate_unique(dentry, inode);
+        if (result) {
+                dput(dentry);
+                dentry = result;
+        }
+
+        return dentry;
+}
+
+static void *proc_ns_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+        struct inode *inode = dentry->d_inode;
+        struct super_block *sb = inode->i_sb;
+        struct proc_inode *ei = PROC_I(inode);
+        struct task_struct *task;
+        struct dentry *ns_dentry;
+        void *error = ERR_PTR(-EACCES);
+
+        task = get_proc_task(inode);
+        if (!task)
+                goto out;
+
+        if (!ptrace_may_access(task, PTRACE_MODE_READ))
+                goto out_put_task;
+
+        ns_dentry = proc_ns_get_dentry(sb, task, ei->ns_ops);
+        if (IS_ERR(ns_dentry)) {
+                error = ERR_CAST(ns_dentry);
+                goto out_put_task;
+        }
+
+        dput(nd->path.dentry);
+        nd->path.dentry = ns_dentry;
+        error = NULL;
+
+out_put_task:
+        put_task_struct(task);
+out:
+        return error;
+}
+
+static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+        struct inode *inode = dentry->d_inode;
+        struct proc_inode *ei = PROC_I(inode);
+        const struct proc_ns_operations *ns_ops = ei->ns_ops;
+        struct task_struct *task;
+        void *ns;
+        char name[50];
+        int len = -EACCES;
+
+        task = get_proc_task(inode);
+        if (!task)
+                goto out;
+
+        if (!ptrace_may_access(task, PTRACE_MODE_READ))
+                goto out_put_task;
+
+        len = -ENOENT;
+        ns = ns_ops->get(task);
+        if (!ns)
+                goto out_put_task;
+
+        snprintf(name, sizeof(name), "%s", ns_ops->name);
+        len = strlen(name);
+
+        if (len > buflen)
+                len = buflen;
+        if (copy_to_user(buffer, ns_ops->name, len))
+                len = -EFAULT;
+
+        ns_ops->put(ns);
+out_put_task:
+        put_task_struct(task);
+out:
+        return len;
+}
+
+static const struct inode_operations proc_ns_link_inode_operations = {
+        .readlink       = proc_ns_readlink,
+        .follow_link    = proc_ns_follow_link,
+        .setattr        = proc_setattr,
+};
+
 static struct dentry *proc_ns_instantiate(struct inode *dir,
         struct dentry *dentry, struct task_struct *task, const void *ptr)
 {
@@ -45,21 +190,15 @@ static struct dentry *proc_ns_instantiate(struct inode *dir,
         struct inode *inode;
         struct proc_inode *ei;
         struct dentry *error = ERR_PTR(-ENOENT);
-        void *ns;
 
         inode = proc_pid_make_inode(dir->i_sb, task);
         if (!inode)
                 goto out;
 
-        ns = ns_ops->get(task);
-        if (!ns)
-                goto out_iput;
-
         ei = PROC_I(inode);
-        inode->i_mode = S_IFREG|S_IRUSR;
-        inode->i_fop  = &ns_file_operations;
-        ei->ns_ops    = ns_ops;
-        ei->ns        = ns;
+        inode->i_mode = S_IFLNK|S_IRWXUGO;
+        inode->i_op = &proc_ns_link_inode_operations;
+        ei->ns_ops = ns_ops;
 
         d_set_d_op(dentry, &pid_dentry_operations);
         d_add(dentry, inode);
@@ -68,9 +207,6 @@ static struct dentry *proc_ns_instantiate(struct inode *dir,
                 error = NULL;
 out:
         return error;
-out_iput:
-        iput(inode);
-        goto out;
 }
 
 static int proc_ns_fill_cache(struct file *filp, void *dirent,
@@ -97,10 +233,6 @@ static int proc_ns_dir_readdir(struct file *filp, void *dirent,
         if (!task)
                 goto out_no_task;
 
-        ret = -EPERM;
-        if (!ptrace_may_access(task, PTRACE_MODE_READ))
-                goto out;
-
         ret = 0;
         i = filp->f_pos;
         switch (i) {
@@ -160,10 +292,6 @@ static struct dentry *proc_ns_dir_lookup(struct inode *dir,
         if (!task)
                 goto out_no_task;
 
-        error = ERR_PTR(-EPERM);
-        if (!ptrace_may_access(task, PTRACE_MODE_READ))
-                goto out;
-
         last = &ns_entries[ARRAY_SIZE(ns_entries)];
         for (entry = ns_entries; entry < last; entry++) {
                 if (strlen((*entry)->name) != len)
@@ -171,7 +299,6 @@ static struct dentry *proc_ns_dir_lookup(struct inode *dir,
                 if (!memcmp(dentry->d_name.name, (*entry)->name, len))
                         break;
         }
-        error = ERR_PTR(-ENOENT);
         if (entry == last)
                 goto out;