Le jeu. 27 août 2020 13:47, P J P <ppandit@redhat.com> a écrit :

> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> While cancelling an i/o operation via ide_cancel_dma_sync(),
> check for null block pointer before calling blk_drain(). Avoid
> null pointer dereference.
>
>  ->
> https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=%2Fide_nullptr1
>     ==1803100==Hint: address points to the zero page.
>     #0 blk_bs ../block/block-backend.c:714
>     #1 blk_drain ../block/block-backend.c:1715
>     #2 ide_cancel_dma_sync ../hw/ide/core.c:723
>     #3 bmdma_cmd_writeb ../hw/ide/pci.c:298
>     #4 bmdma_write ../hw/ide/piix.c:75
>     #5 memory_region_write_accessor ../softmmu/memory.c:483
>     #6 access_with_adjusted_size ../softmmu/memory.c:544
>     #7 memory_region_dispatch_write ../softmmu/memory.c:1465
>     #8 flatview_write_continue ../exec.c:3176
>     ...
>
> Reported-by: Ruhr-University <bugs-syssec@rub.de>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/ide/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index d997a78e47..038af1cd6b 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -718,7 +718,7 @@ void ide_cancel_dma_sync(IDEState *s)
>       * whole DMA operation will be submitted to disk with a single
>       * aio operation with preadv/pwritev.
>       */
> -    if (s->bus->dma->aiocb) {
> +    if (s->blk && s->bus->dma->aiocb) {
>

But s->blk mustn't be null here... IMHO we should assert() here and add a
check earlier.

Don't we already have a Launchpad bug for this BTW?

         trace_ide_cancel_dma_sync_remaining();
>          blk_drain(s->blk);
>          assert(s->bus->dma->aiocb == NULL);
> --
> 2.26.2
>
>
>