From 81c219ac6ce0d6182e35f3976f2caa4cefcaf9f0 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 5 Jun 2017 15:38:43 -0500 Subject: block: Guarantee that *file is set on bdrv_get_block_status() 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. Messed up 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 on all paths that return 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 broken caller that blindly dereferences file without checking for error is now more likely to get a reliable SEGV instead of randomly acting on garbage, making it easier to diagnose such buggy callers. Adding an assertion that file is set where expected doesn't hurt either. CC: qemu-stable@nongnu.org Signed-off-by: Eric Blake Reviewed-by: Fam Zheng Reviewed-by: Max Reitz Reviewed-by: John Snow Signed-off-by: Kevin Wolf --- tests/qemu-iotests/177 | 3 +++ tests/qemu-iotests/177.out | 2 ++ 2 files changed, 5 insertions(+) (limited to 'tests') 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..fcfbfa3 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 json:{"image": {"driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/t.IMGFMT"}}, "driver": "blkdebug", "align": "4k"} No errors were found on the image. *** done -- cgit v1.1