From: Oleg Nesterov <oleg@redhat.com>
Date: Fri, 10 Jul 2009 01:27:40 +0000 (+0200)
Subject: mm_for_maps: take ->cred_guard_mutex to fix the race with exec
X-Git-Tag: v2.6.31-rc6~23^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=704b836cbf19e885f8366bccb2e4b0474346c02d;p=pandora-kernel.git

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>
---

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