tree e9d2fdd79a14e756b20ff2f3a8aa28a93cfa0fce
parent e1f29d0c4ca16aac26a7e86f20068d2b5386af9a
author Oleg Nesterov <oleg@redhat.com> 1446856206 -0800
committer Patrick Tjin <pattjin@google.com> 1454605922 -0800

UPSTREAM: proc: actually make proc_fd_permission() thread-friendly

(cherry pick from commit 54708d2858e79a2bdda10bf8a20c80eb96c20613)

The commit 96d0df79f264 ("proc: make proc_fd_permission() thread-friendly")
fixed the access to /proc/self/fd from sub-threads, but introduced another
problem: a sub-thread can't access /proc/<tid>/fd/ or /proc/thread-self/fd
if generic_permission() fails.

Change proc_fd_permission() to check same_thread_group(pid_task(), current).

Fixes: 96d0df79f264 ("proc: make proc_fd_permission() thread-friendly")
Reported-by: "Jin, Yihua" <yihua.jin@intel.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Bug: 26016905
Change-Id: I1894c78d0b13f0bde8cde84bd142ba67590dc0f1