xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

tmpfs: fix shared mempolicy leak

Browse Source 
This fixes a regression in 3.7-rc, which has since gone into stable.

Commit 00442ad04a ("mempolicy: fix a memory corruption by refcount
imbalance in alloc_pages_vma()") changed get_vma_policy() to raise the
refcount on a shmem shared mempolicy; whereas shmem_alloc_page() went
on expecting alloc_page_vma() to drop the refcount it had acquired.
This deserves a rework: but for now fix the leak in shmem_alloc_page().

Hugh: shmem_swapin() did not need a fix, but surely it's clearer to use
the same refcounting there as in shmem_alloc_page(), delete its onstack
mempolicy, and the strange mpol_cond_copy() and __mpol_cond_copy() -
those were invented to let swapin_readahead() make an unknown number of
calls to alloc_pages_vma() with one mempolicy; but since 00442ad04a,
alloc_pages_vma() has kept refcount in balance, so now no problem.

Reported-and-tested-by: Tommi Rantala <tt.rantala@gmail.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mel Gorman
2012-12-05 14:01:41 -08:00
committed by Linus Torvalds
parent c702418f8a
commit 18a2f371f5
3 changed files with 28 additions and 60 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
mm/mempolicy.c
View File

@@ -2037,28 +2037,6 @@ struct mempolicy *__mpol_dup(struct mempolicy *old)
return new;
}
/*
* If *frompol needs [has] an extra ref, copy *frompol to *tompol ,
* eliminate the * MPOL_F_* flags that require conditional ref and
* [NOTE!!!] drop the extra ref. Not safe to reference *frompol directly
* after return. Use the returned value.
*
* Allows use of a mempolicy for, e.g., multiple allocations with a single
* policy lookup, even if the policy needs/has extra ref on lookup.
* shmem_readahead needs this.
*/
struct mempolicy *__mpol_cond_copy(struct mempolicy *tompol,
struct mempolicy *frompol)
{
if (!mpol_needs_cond_ref(frompol))
return frompol;
*tompol = *frompol;
tompol->flags &= ~MPOL_F_SHARED; /* copy doesn't need unref */
__mpol_put(frompol);
return tompol;
}
/* Slow path of a mempolicy comparison */
bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
{