From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42458) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VXz3N-0000Sn-Eu for qemu-devel@nongnu.org; Sun, 20 Oct 2013 15:52:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VXz3H-0001Hl-Ff for qemu-devel@nongnu.org; Sun, 20 Oct 2013 15:52:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36069) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VXz3H-0001Hg-7a for qemu-devel@nongnu.org; Sun, 20 Oct 2013 15:52:39 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r9KJqcnO025897 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Sun, 20 Oct 2013 15:52:38 -0400 From: Max Reitz Date: Sun, 20 Oct 2013 21:52:35 +0200 Message-Id: <1382298755-21383-1-git-send-email-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH] qcow2: Unset zero_beyond_eof in save_vmstate List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Stefan Hajnoczi , Max Reitz Saving the VM state is done using bdrv_pwrite. This function may perform a read-modify-write, which in this case results in data being read from beyond the end of the virtual disk. Since we are actually trying to access an area which is not a part of the virtual disk, zero_beyond_eof has to be set to false before performing the partial write, otherwise the VM state may become corrupted. Signed-off-by: Max Reitz --- Follow-up to (depends on): - qcow2: Restore total_sectors value in save_vmstate --- block/qcow2.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/qcow2.c b/block/qcow2.c index 5c05bb5..3e11f25 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1941,12 +1941,15 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, BDRVQcowState *s = bs->opaque; int64_t total_sectors = bs->total_sectors; int growable = bs->growable; + bool zero_beyond_eof = bs->zero_beyond_eof; int ret; BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE); bs->growable = 1; + bs->zero_beyond_eof = false; ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov); bs->growable = growable; + bs->zero_beyond_eof = zero_beyond_eof; // bdrv_co_do_writev will have increased the total_sectors value to include // the VM state - the VM state is however not an actual part of the block // device, therefore, we need to restore the old value. -- 1.8.3.1