Re: [PATCH v3] iommu: fix KASAN use-after-free in iommu_insert_resv_region

[Qian Cai]

> On Nov 26, 2019, at 5:27 AM, Eric Auger <eric.auger@xxxxxxxxxx> wrote:
> 
> In case the new region gets merged into another one, the nr
> list node is freed. Checking its type while completing the
> merge algorithm leads to a use-after-free. Use new->type
> instead.
> 
> Fixes: 4dbd258ff63e ("iommu: Revisit iommu_insert_resv_region()
> implementation")
> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
> Reported-by: Qian Cai <cai@xxxxxx>
> Cc: Stable <stable@xxxxxxxxxxxxxxx> #v5.3+


Looks like Joerg is away for a few weeks. Could Andrew or Linus pick up this 
use-after-free?

> 
> ---
> 
> v2 -> v3:
> - directly use new->type
> 
> v1 -> v2:
> - remove spurious new line
> ---
> drivers/iommu/iommu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index d658c7c6a2ab..285ad4a4c7f2 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -313,7 +313,7 @@ int iommu_insert_resv_region(struct iommu_resv_region *new,
> 		phys_addr_t top_end, iter_end = iter->start + iter->length - 1;
> 
> 		/* no merge needed on elements of different types than @nr */
> -		if (iter->type != nr->type) {
> +		if (iter->type != new->type) {
> 			list_move_tail(&iter->list, &stack);
> 			continue;
> 		}
> -- 
> 2.20.1
>