proc: proper pidns handling for /proc/self

Currently if you access a /proc that is not mounted with your processes
current pid namespace /proc/self will point at a completely random task.

This patch fixes /proc/self to point to the current process if it is
available in the particular mount of /proc or to return -ENOENT if the
current process is not visible.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8a19a8a1a3e6f306fab1d6721c4d019828674349..75b1979749a579c34720002f44dde9ed42bf43d9 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2101,15 +2101,23 @@ static const struct file_operations proc_coredump_filter_operations = {
 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
                              int buflen)
 {
+       struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+       pid_t tgid = task_tgid_nr_ns(current, ns);
        char tmp[PROC_NUMBUF];
-       sprintf(tmp, "%d", task_tgid_vnr(current));
+       if (!tgid)
+               return -ENOENT;
+       sprintf(tmp, "%d", tgid);
        return vfs_readlink(dentry,buffer,buflen,tmp);
 }
 
 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
+       struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+       pid_t tgid = task_tgid_nr_ns(current, ns);
        char tmp[PROC_NUMBUF];
-       sprintf(tmp, "%d", task_tgid_vnr(current));
+       if (!tgid)
+               return ERR_PTR(-ENOENT);
+       sprintf(tmp, "%d", task_tgid_nr_ns(current, ns));
        return ERR_PTR(vfs_follow_link(nd,tmp));
 }