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

[Stefan Hajnoczi]

On Fri, Jul 14, 2017 at 03:30:29PM +0530, P J P wrote:
> From: Prasad J Pandit <address@hidden>
> 
> 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.

Please include details on how to reproduce the bug and/or which code
path triggers this NULL dereference.

> Reported-by: Chensongnian <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
>  hw/ide/core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index 0b48b64..04474b3 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -681,8 +681,10 @@ void ide_cancel_dma_sync(IDEState *s)
>  #ifdef DEBUG_IDE
>          printf("%s: draining all remaining requests", __func__);
>  #endif
> -        blk_drain(s->blk);
> -        assert(s->bus->dma->aiocb == NULL);
> +        if (s->blk) {
> +            blk_drain(s->blk);
> +            assert(s->bus->dma->aiocb == NULL);
> +        }
>      }
>  }
>  
> -- 
> 2.9.4
> 
>

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