On 06/05/2017 04:38 PM, Eric Blake wrote: > 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-sta...@nongnu.org > Signed-off-by: Eric Blake <ebl...@redhat.com> > Reviewed-by: Fam Zheng <f...@redhat.com> > Reviewed-by: Max Reitz <mre...@redhat.com>
Reviewed-by: John Snow <js...@redhat.com>
