Re: [Qemu-devel] [Qemu-block] [PATCH v1] ide: check BlockBackend object in ide_cancel_dma_sync

[Kevin Wolf <kwolf@redhat.com>]

Am 17.07.2017 um 15:01 hat P J P geschrieben:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> When cancelling pending DMA requests in ide_cancel_dma_sync,
> the s->blk object could be null, leading to a null dereference.
> Add check to avoid it.
> 
>   blk_bs (blk=0x0) at block/block-backend.c:389
>   blk_drain (blk=0x0) at block/block-backend.c:1232
>   ide_cancel_dma_sync (s=0x7f203241c1a8) at hw/ide/core.c:684
>   bmdma_cmd_writeb (bm=0x7f203241cf20, val=104) at hw/ide/pci.c:237
>   bmdma_write (opaque=0x7f203241cf20, addr=0, val=104, size=1) at hw/ide/piix.c:77
> 
> Reported-by: Chensongnian <chensongnian@huawei.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/ide/core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> Update: add call stack trace leading the null dereference.

I think Stefan didn't only mean a stack trace, but an actual instruction
how to reproduce this. VM configuration, what actions to take, etc.

In fact, I will add that we will probably want a qtest case as a
regression test anyway, and tests are always great for describing how to
reproduce a problem, too.

Kevin