tree 126fe11368da94f0c2e11ed586a870fa1b02f0a6
parent 084f71ae5ceeb16734d8ac47559d3c718456a865
author Johannes Weiner <hannes@cmpxchg.org> 1231281631 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1231286350 -0800

mm: check for no mmaps in exit_mmap()

When dup_mmap() ooms we can end up with mm->mmap == NULL.  The error
path does mmput() and unmap_vmas() gets a NULL vma which it
dereferences.

In exit_mmap() there is nothing to do at all for this case, we can
cancel the callpath right there.

[akpm@linux-foundation.org: add sorely-needed comment]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>