1 files changed, 196 insertions, 9 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 286a422f440e..bd7a9affc14b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -196,18 +196,205 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
         return result;
 }
 
-static int proc_pid_cmdline(struct seq_file *m, struct pid_namespace *ns,
-                            struct pid *pid, struct task_struct *task)
+static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
+                                     size_t _count, loff_t *pos)
 {
+        struct task_struct *tsk;
+        struct mm_struct *mm;
+        char *page;
+        unsigned long count = _count;
+        unsigned long arg_start, arg_end, env_start, env_end;
+        unsigned long len1, len2, len;
+        unsigned long p;
+        char c;
+        ssize_t rv;
+
+        BUG_ON(*pos < 0);
+
+        tsk = get_proc_task(file_inode(file));
+        if (!tsk)
+                return -ESRCH;
+        mm = get_task_mm(tsk);
+        put_task_struct(tsk);
+        if (!mm)
+                return 0;
+        /* Check if process spawned far enough to have cmdline. */
+        if (!mm->env_end) {
+                rv = 0;
+                goto out_mmput;
+        }
+
+        page = (char *)__get_free_page(GFP_TEMPORARY);
+        if (!page) {
+                rv = -ENOMEM;
+                goto out_mmput;
+        }
+
+        down_read(&mm->mmap_sem);
+        arg_start = mm->arg_start;
+        arg_end = mm->arg_end;
+        env_start = mm->env_start;
+        env_end = mm->env_end;
+        up_read(&mm->mmap_sem);
+
+        BUG_ON(arg_start > arg_end);
+        BUG_ON(env_start > env_end);
+
+        len1 = arg_end - arg_start;
+        len2 = env_end - env_start;
+
         /*
-         * Rely on struct seq_operations::show() being called once
-         * per internal buffer allocation. See single_open(), traverse().
+         * Inherently racy -- command line shares address space
+         * with code and data.
          */
-        BUG_ON(m->size < PAGE_SIZE);
-        m->count += get_cmdline(task, m->buf, PAGE_SIZE);
-        return 0;
+        rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0);
+        if (rv <= 0)
+                goto out_free_page;
+
+        rv = 0;
+
+        if (c == '\0') {
+                /* Command line (set of strings) occupies whole ARGV. */
+                if (len1 <= *pos)
+                        goto out_free_page;
+
+                p = arg_start + *pos;
+                len = len1 - *pos;
+                while (count > 0 && len > 0) {
+                        unsigned int _count;
+                        int nr_read;
+
+                        _count = min3(count, len, PAGE_SIZE);
+                        nr_read = access_remote_vm(mm, p, page, _count, 0);
+                        if (nr_read < 0)
+                                rv = nr_read;
+                        if (nr_read <= 0)
+                                goto out_free_page;
+
+                        if (copy_to_user(buf, page, nr_read)) {
+                                rv = -EFAULT;
+                                goto out_free_page;
+                        }
+
+                        p       += nr_read;
+                        len     -= nr_read;
+                        buf     += nr_read;
+                        count   -= nr_read;
+                        rv      += nr_read;
+                }
+        } else {
+                /*
+                 * Command line (1 string) occupies ARGV and maybe
+                 * extends into ENVP.
+                 */
+                if (len1 + len2 <= *pos)
+                        goto skip_argv_envp;
+                if (len1 <= *pos)
+                        goto skip_argv;
+
+                p = arg_start + *pos;
+                len = len1 - *pos;
+                while (count > 0 && len > 0) {
+                        unsigned int _count, l;
+                        int nr_read;
+                        bool final;
+
+                        _count = min3(count, len, PAGE_SIZE);
+                        nr_read = access_remote_vm(mm, p, page, _count, 0);
+                        if (nr_read < 0)
+                                rv = nr_read;
+                        if (nr_read <= 0)
+                                goto out_free_page;
+
+                        /*
+                         * Command line can be shorter than whole ARGV
+                         * even if last "marker" byte says it is not.
+                         */
+                        final = false;
+                        l = strnlen(page, nr_read);
+                        if (l < nr_read) {
+                                nr_read = l;
+                                final = true;
+                        }
+
+                        if (copy_to_user(buf, page, nr_read)) {
+                                rv = -EFAULT;
+                                goto out_free_page;
+                        }
+
+                        p       += nr_read;
+                        len     -= nr_read;
+                        buf     += nr_read;
+                        count   -= nr_read;
+                        rv      += nr_read;
+
+                        if (final)
+                                goto out_free_page;
+                }
+skip_argv:
+                /*
+                 * Command line (1 string) occupies ARGV and
+                 * extends into ENVP.
+                 */
+                if (len1 <= *pos) {
+                        p = env_start + *pos - len1;
+                        len = len1 + len2 - *pos;
+                } else {
+                        p = env_start;
+                        len = len2;
+                }
+                while (count > 0 && len > 0) {
+                        unsigned int _count, l;
+                        int nr_read;
+                        bool final;
+
+                        _count = min3(count, len, PAGE_SIZE);
+                        nr_read = access_remote_vm(mm, p, page, _count, 0);
+                        if (nr_read < 0)
+                                rv = nr_read;
+                        if (nr_read <= 0)
+                                goto out_free_page;
+
+                        /* Find EOS. */
+                        final = false;
+                        l = strnlen(page, nr_read);
+                        if (l < nr_read) {
+                                nr_read = l;
+                                final = true;
+                        }
+
+                        if (copy_to_user(buf, page, nr_read)) {
+                                rv = -EFAULT;
+                                goto out_free_page;
+                        }
+
+                        p       += nr_read;
+                        len     -= nr_read;
+                        buf     += nr_read;
+                        count   -= nr_read;
+                        rv      += nr_read;
+
+                        if (final)
+                                goto out_free_page;
+                }
+skip_argv_envp:
+                ;
+        }
+
+out_free_page:
+        free_page((unsigned long)page);
+out_mmput:
+        mmput(mm);
+        if (rv > 0)
+                *pos += rv;
+        return rv;
 }
 
+static const struct file_operations proc_pid_cmdline_ops = {
+        .read   = proc_pid_cmdline_read,
+        .llseek = generic_file_llseek,
+};
+
 static int proc_pid_auxv(struct seq_file *m, struct pid_namespace *ns,
                          struct pid *pid, struct task_struct *task)
 {
@@ -2572,7 +2759,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
         ONE("syscall",    S_IRUSR, proc_pid_syscall),
 #endif
-        ONE("cmdline",    S_IRUGO, proc_pid_cmdline),
+        REG("cmdline",    S_IRUGO, proc_pid_cmdline_ops),
         ONE("stat",       S_IRUGO, proc_tgid_stat),
         ONE("statm",      S_IRUGO, proc_pid_statm),
         REG("maps",       S_IRUGO, proc_pid_maps_operations),
@@ -2918,7 +3105,7 @@ static const struct pid_entry tid_base_stuff[] = {
 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
         ONE("syscall",   S_IRUSR, proc_pid_syscall),
 #endif
-        ONE("cmdline",   S_IRUGO, proc_pid_cmdline),
+        REG("cmdline",   S_IRUGO, proc_pid_cmdline_ops),
         ONE("stat",      S_IRUGO, proc_tid_stat),
         ONE("statm",     S_IRUGO, proc_pid_statm),
         REG("maps",      S_IRUGO, proc_tid_maps_operations),