Re: [RFC PATCH-for-5.1 v2] hw/ide: Cancel pending DMA requests before setting as inactive

[Philippe Mathieu-Daudé]

On 7/17/20 9:53 AM, Philippe Mathieu-Daudé wrote:
> libFuzzer found a case where requests are queued for later in the
> AIO context, but a command set the bus inactive, then when finally
> the requests are processed by the DMA it aborts because it is
> inactive:
> 
>  include/hw/ide/pci.h:59: IDEState *bmdma_active_if(BMDMAState *): Assertion 
> `bmdma->bus->retry_unit != (uint8_t)-1' failed.
> 
> Reproducer available on the BugLink.
> 
> Fix by draining the pending DMA requests before inactivating the bus.
> 

Fixes: 8ccad811e6 ("use AIO for DMA transfers - enabled DMA for CDROMs")

> BugLink: https://bugs.launchpad.net/qemu/+bug/1887303
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> RFC because I don't have much clue about block drive and IDE,
> so block-team please be very careful while reviewing this bug.
> ---
>  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..f7affafb0c 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -804,7 +804,7 @@ void dma_buf_commit(IDEState *s, uint32_t tx_bytes)
>  
>  void ide_set_inactive(IDEState *s, bool more)
>  {
> -    s->bus->dma->aiocb = NULL;
> +    ide_cancel_dma_sync(s);
>      ide_clear_retry(s);
>      if (s->bus->dma->ops->set_inactive) {
>          s->bus->dma->ops->set_inactive(s->bus->dma, more);
>