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| author | Vlastimil Babka <vbabka@suse.cz> | 2014-04-07 15:37:50 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2014-04-30 16:23:26 +0100 |
| commit | 8e8836abf74a0b227c651cf76466b8d711470a76 (patch) | |
| tree | 9fa012c753cb4e325b4e13f70cad06178c4e53a6 /mm/mlock.c | |
| parent | 9acd41220b5addaf9d59b1e8825375d34803a375 (diff) | |
| download | kernel_samsung_smdk4412-8e8836abf74a0b227c651cf76466b8d711470a76.zip kernel_samsung_smdk4412-8e8836abf74a0b227c651cf76466b8d711470a76.tar.gz kernel_samsung_smdk4412-8e8836abf74a0b227c651cf76466b8d711470a76.tar.bz2 | |
mm: try_to_unmap_cluster() should lock_page() before mlocking
commit 57e68e9cd65b4b8eb4045a1e0d0746458502554c upstream.
A BUG_ON(!PageLocked) was triggered in mlock_vma_page() by Sasha Levin
fuzzing with trinity. The call site try_to_unmap_cluster() does not lock
the pages other than its check_page parameter (which is already locked).
The BUG_ON in mlock_vma_page() is not documented and its purpose is
somewhat unclear, but apparently it serializes against page migration,
which could otherwise fail to transfer the PG_mlocked flag. This would
not be fatal, as the page would be eventually encountered again, but
NR_MLOCK accounting would become distorted nevertheless. This patch adds
a comment to the BUG_ON in mlock_vma_page() and munlock_vma_page() to that
effect.
The call site try_to_unmap_cluster() is fixed so that for page !=
check_page, trylock_page() is attempted (to avoid possible deadlocks as we
already have check_page locked) and mlock_vma_page() is performed only
upon success. If the page lock cannot be obtained, the page is left
without PG_mlocked, which is again not a problem in the whole unevictable
memory design.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'mm/mlock.c')
| -rw-r--r-- | mm/mlock.c | 2 |
1 files changed, 2 insertions, 0 deletions
@@ -78,6 +78,7 @@ void __clear_page_mlock(struct page *page) */ void mlock_vma_page(struct page *page) { + /* Serialize with page migration */ BUG_ON(!PageLocked(page)); if (!TestSetPageMlocked(page)) { @@ -105,6 +106,7 @@ void mlock_vma_page(struct page *page) */ void munlock_vma_page(struct page *page) { + /* For try_to_munlock() and to serialize with page migration */ BUG_ON(!PageLocked(page)); if (TestClearPageMlocked(page)) { |