[PATCH] powerpc/book3s64: Fix error handling in mm_iommu_do_alloc()

[Alexey Kardashevskiy]

On 11/12/2019 21:42, Jan Kara wrote:
> The last jump to free_exit in mm_iommu_do_alloc() happens after page
> pointers in struct mm_iommu_table_group_mem_t were already converted to
> physical addresses. Thus calling put_page() on these physical addresses
> will likely crash. Convert physical addresses back to page pointers
> during the error cleanup.
> 
> Signed-off-by: Jan Kara <jack at suse.cz>
> ---
>  arch/powerpc/mm/book3s64/iommu_api.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
>  Beware, this is completely untested, spotted just by code audit.
> 
> diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
> index 56cc84520577..06c403381c9c 100644
> --- a/arch/powerpc/mm/book3s64/iommu_api.c
> +++ b/arch/powerpc/mm/book3s64/iommu_api.c
> @@ -154,7 +154,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
>  				       (mem2->entries << PAGE_SHIFT)))) {
>  			ret = -EINVAL;
>  			mutex_unlock(&mem_list_mutex);
> -			goto free_exit;
> +			goto convert_exit;
>  		}
>  	}
>  
> @@ -166,6 +166,9 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
>  
>  	return 0;
>  
> +convert_exit:
> +	for (i = 0; i < pinned; i++)
> +		mem->hpages[i] = pfn_to_page(mem->hpas[i] >> PAGE_SHIFT);


Good find. Although doing it where you added "goto convert_exit" seems
cleaner imho. Thanks,


>  free_exit:
>  	/* free the reference taken */
>  	for (i = 0; i < pinned; i++)
> 

-- 
Alexey