From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35327) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dX5eo-0004X3-Ly for qemu-devel@nongnu.org; Mon, 17 Jul 2017 09:01:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dX5en-0000wC-AT for qemu-devel@nongnu.org; Mon, 17 Jul 2017 09:01:50 -0400 From: P J P Date: Mon, 17 Jul 2017 18:31:30 +0530 Message-Id: <20170717130130.29211-1-ppandit@redhat.com> Subject: [Qemu-devel] [PATCH v1] ide: check BlockBackend object in ide_cancel_dma_sync List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Qemu Developers Cc: Stefan Hajnoczi , John Snow , Chensongnian , qemu-block@nongnu.org, Prasad J Pandit From: Prasad J Pandit When cancelling pending DMA requests in ide_cancel_dma_sync, the s->blk object could be null, leading to a null dereference. Add check to avoid it. blk_bs (blk=0x0) at block/block-backend.c:389 blk_drain (blk=0x0) at block/block-backend.c:1232 ide_cancel_dma_sync (s=0x7f203241c1a8) at hw/ide/core.c:684 bmdma_cmd_writeb (bm=0x7f203241cf20, val=104) at hw/ide/pci.c:237 bmdma_write (opaque=0x7f203241cf20, addr=0, val=104, size=1) at hw/ide/piix.c:77 Reported-by: Chensongnian Signed-off-by: Prasad J Pandit --- hw/ide/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) Update: add call stack trace leading the null dereference. diff --git a/hw/ide/core.c b/hw/ide/core.c index 0b48b64..04474b3 100644 --- a/hw/ide/core.c +++ b/hw/ide/core.c @@ -681,8 +681,10 @@ void ide_cancel_dma_sync(IDEState *s) #ifdef DEBUG_IDE printf("%s: draining all remaining requests", __func__); #endif - blk_drain(s->blk); - assert(s->bus->dma->aiocb == NULL); + if (s->blk) { + blk_drain(s->blk); + assert(s->bus->dma->aiocb == NULL); + } } } -- 2.9.4