Re: [PATCH] hw: ide: check the pointer before do dma memory unmap

[Alexander Bulekov <alxndr@bu.edu>]

On 200815 0020, Li Qiang wrote:
> In 'map_page' we need to check the return value of
> 'dma_memory_map' to ensure the we actully maped something.
> Otherwise, we will hit an assert in 'address_space_unmap'.
> This is because we can't find the MR with the NULL buffer.
> This is the LP#1884693:
> 
> -->https://bugs.launchpad.net/qemu/+bug/1884693
> 
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Signed-off-by: Li Qiang <liq3ea@163.com>

I'm not very familiar with the IDE code, but this seems like a simple
null-ptr check, and Li has not received a response in over a month.

Reviewed-by: Alexander Bulekov <alxndr@bu.edu>

> ---
>  hw/ide/ahci.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index 009120f88b..63e9fccdbe 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -250,6 +250,11 @@ static void map_page(AddressSpace *as, uint8_t **ptr, uint64_t addr,
>      }
>  
>      *ptr = dma_memory_map(as, addr, &len, DMA_DIRECTION_FROM_DEVICE);
> +
> +    if (!*ptr) {
> +        return;
> +    }
> +
>      if (len < wanted) {
>          dma_memory_unmap(as, *ptr, len, DMA_DIRECTION_FROM_DEVICE, len);
>          *ptr = NULL;
> -- 
> 2.17.1
>