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authorMing Lei <ming.lei@canonical.com>2013-10-31 16:34:17 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-10-31 16:58:13 -0700
commit3d77b50c5874b7e923be946ba793644f82336b75 (patch)
treeac769dcd6c5492b65353c7bdcc923c1530f9066a
parent696ac172fffa653dca401bb2b0cad91cf2ce453f (diff)
downloadlinux-3d77b50c5874b7e923be946ba793644f82336b75.tar.gz
lib/scatterlist.c: don't flush_kernel_dcache_page on slab page
Commit b1adaf65ba03 ("[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> Cc: <stable@vger.kernel.org> [3.2+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/scatterlist.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index a685c8a7957..d16fa295ae1 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -577,7 +577,8 @@ void sg_miter_stop(struct sg_mapping_iter *miter)
miter->__offset += miter->consumed;
miter->__remaining -= 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);
if (miter->__flags & SG_MITER_ATOMIC) {