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

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Date:   Tue, 26 Nov 2019 10:19:04 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, joro@...tes.org, hch@....de, cai@....pw,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] iommu: fix KASAN use-after-free in
 iommu_insert_resv_region

On Tue Nov 26 19, Eric Auger 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@...hat.com>
>Reported-by: Qian Cai <cai@....pw>
>Cc: Stable <stable@...r.kernel.org> #v5.3+
>

Minor nit, but should the comment above list_for_each_entry_safe get
updated as well? Other than that, lgtm.

Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>

>---
>
>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
>
>_______________________________________________
>iommu mailing list
>iommu@...ts.linux-foundation.org
>https://lists.linuxfoundation.org/mailman/listinfo/iommu
>

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