From: Vladimir Davydov <vdavydov@parallels.com>
Date: Fri, 8 Aug 2014 21:22:01 +0000 (-0700)
Subject: fork: copy mm's vm usage counters under mmap_sem
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~116^2~117
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4f7d461433bb4a4deee61baefdac6cd1a1ecb546;p=pandora-kernel.git

fork: copy mm's vm usage counters under mmap_sem

If a forking process has a thread calling (un)mmap (silly but still),
the child process may have some of its mm's vm usage counters (total_vm
and friends) screwed up, because currently they are copied from oldmm
w/o holding any locks (memcpy in dup_mm).

This patch moves the counters initialization to dup_mmap() to be called
under oldmm->mmap_sem, which eliminates any possibility of race.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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