Commit c6caeb7c authored Feb 08, 2008 by Eric W. Biederman Committed by Linus Torvalds Feb 08, 2008

proc: fix the threaded /proc/self



Long ago when the CLONE_THREAD support first went it someone thought it
would be wise to point /proc/self at /proc/<tgid> instead of /proc/<pid>.

Given that /proc/<tgid> can return information about a very different task
(if enough things have been unshared) then our current process /proc/<tgid>
seems blatantly wrong.  So far I have yet to think up an example where the
current behavior would be advantageous, and I can see several places where
it is seriously non-intuitive.

We may be stuck with the current broken behavior for backwards
compatibility reasons but lets try fixing our ancient bug for the 2.6.25
time frame and see if anyone screams.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: "Guillaume Chazarain" <guichaz@yahoo.fr>
Cc: "Pavel Emelyanov" <xemul@openvz.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 488e5bc4

fs/proc/base.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -2102,22 +2102,22 @@ 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);
		pid_t pid = task_pid_nr_ns(current, ns);
		char tmp[PROC_NUMBUF];
		if (!tgid)
		if (!pid)
		return -ENOENT;
		sprintf(tmp, "%d", tgid);
		sprintf(tmp, "%d", pid);
		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);
		pid_t pid = task_pid_nr_ns(current, ns);
		char tmp[PROC_NUMBUF];
		if (!tgid)
		if (!pid)
		return ERR_PTR(-ENOENT);
		sprintf(tmp, "%d", task_tgid_nr_ns(current, ns));
		sprintf(tmp, "%d", pid);
		return ERR_PTR(vfs_follow_link(nd,tmp));
		}

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