tree fe3609c5e750d4a06876f61ab217503e56b4e182
parent ce65cefa5debefc0e81d0a533bda467f0aa67350
author Vladimir Davydov <vdavydov@parallels.com> 1407532921 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1407538643 -0700

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>