From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Ming Lei , Russell King - ARM Linux , Will Deacon , Aaro Koskinen , FUJITA Tomonori , Tejun Heo , "James E.J. Bottomley" , Jens Axboe , Andrew Morton , Linus Torvalds , Kamal Mostafa Subject: [PATCH 3.8 90/91] lib/scatterlist.c: don't flush_kernel_dcache_page on slab page Date: Thu, 7 Nov 2013 18:15:45 -0800 Message-Id: <1383876946-2396-91-git-send-email-kamal@canonical.com> In-Reply-To: <1383876946-2396-1-git-send-email-kamal@canonical.com> References: <1383876946-2396-1-git-send-email-kamal@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.8.13.13 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Ming Lei 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 Reported-by: Aaro Koskinen Tested-by: Simon Baatz Cc: Russell King - ARM Linux Cc: Will Deacon Cc: Aaro Koskinen Acked-by: Catalin Marinas Cc: FUJITA Tomonori Cc: Tejun Heo Cc: "James E.J. Bottomley" Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Kamal Mostafa --- 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