From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=36651 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PnYmI-0000WG-OO for qemu-devel@nongnu.org; Thu, 10 Feb 2011 10:49:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PnYmA-0007xr-6s for qemu-devel@nongnu.org; Thu, 10 Feb 2011 10:49:47 -0500 Received: from mx1.redhat.com ([209.132.183.28]:9644) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PnYm9-0007xW-Ps for qemu-devel@nongnu.org; Thu, 10 Feb 2011 10:49:46 -0500 From: Kevin Wolf Date: Thu, 10 Feb 2011 16:51:17 +0100 Message-Id: <1297353086-4844-3-git-send-email-kwolf@redhat.com> In-Reply-To: <1297353086-4844-1-git-send-email-kwolf@redhat.com> References: <1297353086-4844-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 02/11] QCOW2: bug fix - read base image beyond its size List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Chunqiang Tang This patch fixes the following bug in QCOW2. For a QCOW2 image that is larger than its base image, when handling a read request straddling over the end of the base image, the QCOW2 driver attempts to read beyond the end of the base image and the request would fail. This bug was found by Fast Virtual Disk (FVD)'s fully automated testing tool. The following test triggered the bug. dd if=/dev/zero of=/var/ramdisk/truth.raw count=0 bs=1 seek=1098561536 dd if=/dev/zero of=/var/ramdisk/zero-500M.raw count=0 bs=1 seek=593099264 ./qemu-img create -f qcow2 -ocluster_size=65536,backing_fmt=blksim -b /var/ramdisk/zero-500M.raw /var/ramdisk/test.qcow2 1098561536 ./qemu-io --auto --seed=30477694 --truth=/var/ramdisk/truth.raw --format=qcow2 --test=blksim:/var/ramdisk/test.qcow2 --verify_write=true --compare_before=false --compare_after=true --round=100000 --parallel=100 --io_size=10485760 --fail_prob=0 --cancel_prob=0 --instant_qemubh=true Signed-off-by: Chunqiang Tang Signed-off-by: Kevin Wolf --- block/qcow2.c | 5 ++--- cutils.c | 31 +++++++++++++++++++++++++++++++ qemu-common.h | 2 ++ 3 files changed, 35 insertions(+), 3 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index a1773e4..28338bf 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -355,7 +355,7 @@ int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov, else n1 = bs->total_sectors - sector_num; - qemu_iovec_memset(qiov, 0, 512 * (nb_sectors - n1)); + qemu_iovec_memset_skip(qiov, 0, 512 * (nb_sectors - n1), 512 * n1); return n1; } @@ -478,8 +478,7 @@ static void qcow2_aio_read_cb(void *opaque, int ret) if (n1 > 0) { BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO); acb->hd_aiocb = bdrv_aio_readv(bs->backing_hd, acb->sector_num, - &acb->hd_qiov, acb->cur_nr_sectors, - qcow2_aio_read_cb, acb); + &acb->hd_qiov, n1, qcow2_aio_read_cb, acb); if (acb->hd_aiocb == NULL) goto done; } else { diff --git a/cutils.c b/cutils.c index 8d562b2..f9a7e36 100644 --- a/cutils.c +++ b/cutils.c @@ -267,6 +267,37 @@ void qemu_iovec_memset(QEMUIOVector *qiov, int c, size_t count) } } +void qemu_iovec_memset_skip(QEMUIOVector *qiov, int c, size_t count, + size_t skip) +{ + int i; + size_t done; + void *iov_base; + uint64_t iov_len; + + done = 0; + for (i = 0; (i < qiov->niov) && (done != count); i++) { + if (skip >= qiov->iov[i].iov_len) { + /* Skip the whole iov */ + skip -= qiov->iov[i].iov_len; + continue; + } else { + /* Skip only part (or nothing) of the iov */ + iov_base = (uint8_t*) qiov->iov[i].iov_base + skip; + iov_len = qiov->iov[i].iov_len - skip; + skip = 0; + } + + if (done + iov_len > count) { + memset(iov_base, c, count - done); + break; + } else { + memset(iov_base, c, iov_len); + } + done += iov_len; + } +} + #ifndef _WIN32 /* Sets a specific flag */ int fcntl_setfl(int fd, int flag) diff --git a/qemu-common.h b/qemu-common.h index c7ff280..cb4b7e0 100644 --- a/qemu-common.h +++ b/qemu-common.h @@ -322,6 +322,8 @@ void qemu_iovec_reset(QEMUIOVector *qiov); void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf); void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count); void qemu_iovec_memset(QEMUIOVector *qiov, int c, size_t count); +void qemu_iovec_memset_skip(QEMUIOVector *qiov, int c, size_t count, + size_t skip); struct Monitor; typedef struct Monitor Monitor; -- 1.7.2.3