3.8.13.13 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Ming Lei <[email protected]> commit 3d77b50c5874b7e923be946ba793644f82336b75 upstream. 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 <[email protected]> Reported-by: Aaro Koskinen <[email protected]> Tested-by: Simon Baatz <[email protected]> Cc: Russell King - ARM Linux <[email protected]> Cc: Will Deacon <[email protected]> Cc: Aaro Koskinen <[email protected]> Acked-by: Catalin Marinas <[email protected]> Cc: FUJITA Tomonori <[email protected]> Cc: Tejun Heo <[email protected]> Cc: "James E.J. Bottomley" <[email protected]> Cc: Jens Axboe <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- lib/scatterlist.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 7874b01..bd86887 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -495,7 +495,8 @@ void sg_miter_stop(struct sg_mapping_iter *miter) if (miter->addr) { 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); if (miter->__flags & SG_MITER_ATOMIC) { -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
