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lib/scatterlist.c: don't flush_kernel_dcache_page on slab page

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commit 3d77b50c58 upstream.

Commit b1adaf65ba ("[SCSI] block: add sg buffer copy helper
functions") introduces two sg buffer copy helpers, and calls
flush_kernel_dcache_page() on pages in SG list after these pages are
written to.

Unfortunately, the commit may introduce a potential bug:

 - Before sending some SCSI commands, kmalloc() buffer may be passed to
   block layper, so flush_kernel_dcache_page() can see a slab page
   finally

 - According to cachetlb.txt, flush_kernel_dcache_page() is only called
   on "a user page", which surely can't be a slab page.

 - ARCH's implementation of flush_kernel_dcache_page() may use page
   mapping information to do optimization so page_mapping() will see the
   slab page, then VM_BUG_ON() is triggered.

Aaro Koskinen reported the bug on ARM/kirkwood when DEBUG_VM is enabled,
and this patch fixes the bug by adding test of '!PageSlab(miter->page)'
before calling flush_kernel_dcache_page().

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Tested-by: Simon Baatz <gmbnomis@gmail.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <tj@kernel.org>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ming Lei 2013-10-31 16:34:17 -07:00 committed by Greg Kroah-Hartman
parent 10ff8e6bf0
commit 366f8a3ab0
1 changed files with 2 additions and 1 deletions
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3
lib/scatterlist.c
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@ -419,7 +419,8 @@ void sg_miter_stop(struct sg_mapping_iter *miter)
if (miter->addr) { if (miter->addr) {
miter->__offset += miter->consumed; miter->__offset += miter->consumed;
if (miter->__flags & SG_MITER_TO_SG) if ((miter->__flags & SG_MITER_TO_SG) &&
!PageSlab(miter->page))
flush_kernel_dcache_page(miter->page); flush_kernel_dcache_page(miter->page);
if (miter->__flags & SG_MITER_ATOMIC) { if (miter->__flags & SG_MITER_ATOMIC) {