On 27/04/2015 15:18, Fam Zheng wrote: > An unaligned zero write causes NULL deferencing in bdrv_co_do_pwritev. That > path is reachable from bdrv_co_write_zeroes and bdrv_aio_write_zeroes. > > You can easily trigger through the former with qemu-io, as the test case added > by 61815d6e0aa. For bdrv_aio_write_zeroes, in common cases there's always a > format driver (which uses 512 alignment), so it would be much rarer to have > unaligned requests (only concerning top level here, when the request goes down > to bs->file, where for example the alignment is 4k, it would then be calling > bdrv_co_write_zeroes because it's in a coroutine). > > fc3959e4669a1c fixed bdrv_co_write_zeroes but not bdrv_aio_write_zeroes. The > lattern is the actually used one by device model. Revert the previous fix, do > it in bdrv_co_do_pwritev, to cover both paths. > > v4: "if (!qiov)" -> "if (!qiov && bytes >= align)". (Paolo) > > v3: Fix the case where the unaligned request is contained within the first > block. (Paolo) > Also update iotests 033 to cover the code path with qemu-io. > > v2: Split to three aligned pwritev. > > > Fam Zheng (3): > Revert "block: Fix unaligned zero write" > block: Fix NULL deference for unaligned write if qiov is NULL > qemu-iotests: Test unaligned sub-block zero write > > block.c | 123 > +++++++++++++++++++++++++-------------------- > tests/qemu-iotests/033 | 13 +++++ > tests/qemu-iotests/033.out | 30 +++++++++++ > 3 files changed, 111 insertions(+), 55 deletions(-) >
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>