tree 62a312157cd39fbd0a2d7ff4b0bebe7c196c7594
parent d3c8660233d3f2801e14eaf722937ff4ed49bfb7
author Oleg Nesterov <oleg@redhat.com> 1247189260 +0200
committer James Morris <jmorris@namei.org> 1249870868 +1000

mm_for_maps: take ->cred_guard_mutex to fix the race with exec

The problem is minor, but without ->cred_guard_mutex held we can race
with exec() and get the new ->mm but check old creds.

Now we do not need to re-check task->mm after ptrace_may_access(), it
can't be changed to the new mm under us.

Strictly speaking, this also fixes another very minor problem. Unless
security check fails or the task exits mm_for_maps() should never
return NULL, the caller should get either old or new ->mm.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>