There are many existing qcow2 images that specify a backing file but
no format. This has been the source of CVEs in the past, but has
become more prominent of a problem now that libvirt has switched to
-blockdev. With older -drive, at least the probing was always done by
qemu (so the only risk of a changed format between successive boots of
a guest was if qemu was upgraded and probed differently). But with
newer -blockdev, libvirt must specify a format; if libvirt guesses raw
where the image was formatted, this results in data corruption visible
to the guest; conversely, if libvirt guesses qcow2 where qemu was
using raw, this can result in potential security holes, so modern
libvirt instead refuses to use images without explicit backing format.
The change in libvirt to reject images without explicit backing format
has pointed out that a number of tools have been far too reliant on
probing in the past. It's time to set a better example in our own
iotests of properly setting this parameter.
iotest calls to create, rebase, and convert are all impacted to some
degree. It's a bit annoying that we are inconsistent on command line
- while all of those accept -o backing_file=...,backing_fmt=..., the
shortcuts are different: create and rebase have -b and -F, while
convert has -B but no -F. (amend has no shortcuts, but the previous
patch just deprecated the use of amend to change backing chains).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200706203954.341758-9-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When originally written, test 177 explicitly took care to run
with compat=0.10. Then I botched my own test in commit
81c219ac and f0a9c18f, by adding additional actions that require
v3 images. Split out the new code into a new v3-only test, 204,
and revert 177 back to its original state other than a new comment.
Reported-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-id: 20180117165420.15946-2-eblake@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
Previously, the alloc command required that input parameters be
sector-aligned and clamped to 32 bits, because the underlying
bdrv_is_allocated used a 32-bit parameter and asserted aligned
inputs. But now that we have fixed block status to report a
64-bit bytes value, and to properly round requests on behalf of
guests, we can pass any values, and can use qemu-io to add
coverage that our rounding is correct regardless of the guest
alignment constraints.
Update iotest 177 to intentionally probe block status at
unaligned boundaries as well as with a bytes value that does not
map to 32-bit sectors, which also required tweaking the image
prep to leave an unallocated portion to the image under test.
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Without a passthrough status of BDRV_BLOCK_RAW, anything wrapped by
blkdebug appears 100% allocated as data. Better is treating it the
same as the underlying file being wrapped.
Update iotest 177 for the new expected output.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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 <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Use blkdebug's new geometry constraints to emulate setups that
have needed past regression fixes: write zeroes asserting
when running through a loopback block device with max-transfer
smaller than cluster size, and discard rounding away portions
of requests not aligned to preferred boundaries. Also, add
coverage that the block layer is honoring max transfer limits.
For now, a single iotest performs all actions, with the idea
that we can add future blkdebug constraint test cases in the
same file; but it can be split into multiple iotests if we find
reason to run one portion of the test in more setups than what
are possible in the other.
For reference, the final portion of the test (checking whether
discard passes as much as possible to the lowest layers of the
stack) works as follows:
qemu-io: discard 30M at 80000001, passed to blkdebug
blkdebug: discard 511 bytes at 80000001, -ENOTSUP (smaller than
blkdebug's 512 align)
blkdebug: discard 14371328 bytes at 80000512, passed to qcow2
qcow2: discard 739840 bytes at 80000512, -ENOTSUP (smaller than
qcow2's 1M align)
qcow2: discard 13M bytes at 77M, succeeds
blkdebug: discard 15M bytes at 90M, passed to qcow2
qcow2: discard 15M bytes at 90M, succeeds
blkdebug: discard 1356800 bytes at 105M, passed to qcow2
qcow2: discard 1M at 105M, succeeds
qcow2: discard 308224 bytes at 106M, -ENOTSUP (smaller than qcow2's
1M align)
blkdebug: discard 1 byte at 111457280, -ENOTSUP (smaller than
blkdebug's 512 align)
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170429191419.30051-10-eblake@redhat.com
[mreitz: For cooperation with image locking, add -r to the qemu-io
invocation which verifies the image content]
Signed-off-by: Max Reitz <mreitz@redhat.com>
Eric Blake