From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46535) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dBXig-0001mP-Q0 for qemu-devel@nongnu.org; Thu, 18 May 2017 22:32:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dBXif-0002TH-SU for qemu-devel@nongnu.org; Thu, 18 May 2017 22:32:46 -0400 From: Eric Blake Date: Thu, 18 May 2017 21:32:31 -0500 Message-Id: <20170519023233.24461-3-eblake@redhat.com> In-Reply-To: <20170519023233.24461-1-eblake@redhat.com> References: <20170519023233.24461-1-eblake@redhat.com> Subject: [Qemu-devel] [PATCH 2/4] block: Guarantee that *file is set on bdrv_get_block_status() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, jsnow@redhat.com, mreitz@redhat.com, qemu-stable@nongnu.org, Stefan Hajnoczi , Fam Zheng , Kevin Wolf We document that *file is valid if the return is not an error and includes BDRV_BLOCK_OFFSET_VALID, but forgot to obey this contract when a driver (such as blkdebug) lacks a callback. Broken in commit 67a0fd2 (v2.6), when we added the file parameter. Enhance qemu-iotest 177 to cover this, using a sequence that would print garbage or even SEGV, because it was dererefencing through uninitialized memory. [The resulting test output shows that we have less-than-ideal block status from the blkdebug driver, but that's a separate fix coming up soon.] Setting *file only when setting BDRV_BLOCK_OFFSET_VALID is enough to fix the crash, but we can go one step further: always setting *file, even on error, means that a caller is no longer dereferencing uninitialized memory, so that we are more likely to get a reliable SEGV instead of randomly acting on garbage. Adding an assertion doesn't hurt either. CC: qemu-stable@nongnu.org Signed-off-by: Eric Blake --- block/io.c | 4 +++- tests/qemu-iotests/177 | 3 +++ tests/qemu-iotests/177.out | 2 ++ 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/block/io.c b/block/io.c index fdd7485..164a82b 100644 --- a/block/io.c +++ b/block/io.c @@ -1749,6 +1749,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, int64_t n; int64_t ret, ret2; + *file = NULL; total_sectors = bdrv_nb_sectors(bs); if (total_sectors < 0) { return total_sectors; @@ -1769,6 +1770,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED; if (bs->drv->protocol_name) { ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE); + *file = bs; } return ret; } @@ -1783,7 +1785,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, } if (ret & BDRV_BLOCK_RAW) { - assert(ret & BDRV_BLOCK_OFFSET_VALID); + assert(ret & BDRV_BLOCK_OFFSET_VALID && *file); ret = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS, *pnum, pnum, file); goto out; diff --git a/tests/qemu-iotests/177 b/tests/qemu-iotests/177 index 2005c17..f8ed8fb 100755 --- a/tests/qemu-iotests/177 +++ b/tests/qemu-iotests/177 @@ -43,6 +43,7 @@ _supported_proto file CLUSTER_SIZE=1M size=128M options=driver=blkdebug,image.driver=qcow2 +nested_opts=image.file.driver=file,image.file.filename=$TEST_IMG echo echo "== setting up files ==" @@ -106,6 +107,8 @@ function verify_io() } verify_io | $QEMU_IO -r "$TEST_IMG" | _filter_qemu_io +$QEMU_IMG map --image-opts "$options,$nested_opts,align=4k" \ + | _filter_qemu_img_map _check_test_img diff --git a/tests/qemu-iotests/177.out b/tests/qemu-iotests/177.out index e887542..b754ed4 100644 --- a/tests/qemu-iotests/177.out +++ b/tests/qemu-iotests/177.out @@ -45,5 +45,7 @@ read 30408704/30408704 bytes at offset 80740352 29 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) read 23068672/23068672 bytes at offset 111149056 22 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) +Offset Length File +0 0x8000000 blkdebug::TEST_DIR/t.IMGFMT No errors were found on the image. *** done -- 2.9.4