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authorEric Blake <eblake@redhat.com>2017-06-05 15:38:43 -0500
committerKevin Wolf <kwolf@redhat.com>2017-07-10 13:18:05 +0200
commit81c219ac6ce0d6182e35f3976f2caa4cefcaf9f0 (patch)
treea55fe72a3b42d3026d57cec604c5bedbb907622f /include
parent64ebf556486af39024cc9e7a8c88303a7b37c465 (diff)
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 <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>
Diffstat (limited to 'include')
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