Re: [PATCH] swiotlb: Fix uninitialized pointer on DMA ops

[Robin Murphy <robin.murphy@arm.com>]

On 18/08/18 20:04, Esteban Zamora wrote:
> The mmap function pointer on swiotlb_dma_ops struct is
> uninitialized, which causes a random crash when calling
> the dma_mmap_coherent function on platforms where no DMA
> address translation hardware is available.

Can you share any kernel logs with details of those crashes? As Konrad 
mentions, the rules for partial structure initialisation in C are 
well-defined, even with designated initialisers[1], and if this commit 
message were true then half of the subsystems in the kernel would be 
crashing left right and centre.

Robin.

[1] 
https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated-Inits

> Set this pointer to NULL in order to fix the issue.
> 
> Signed-off-by: Esteban Zamora <estebanzacr.20@gmail.com>
> ---
>   kernel/dma/swiotlb.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 4f8a6db..9a7718c 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -1082,5 +1082,6 @@ const struct dma_map_ops swiotlb_dma_ops = {
>   	.map_page		= swiotlb_map_page,
>   	.unmap_page		= swiotlb_unmap_page,
>   	.dma_supported		= dma_direct_supported,
> +	.mmap                   = NULL,
>   };
>   EXPORT_SYMBOL(swiotlb_dma_ops);
>