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

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Message-Id: <0DE725CD-01CD-4E01-B817-9CC7F4768FBC@lca.pw>
Date:   Mon, 16 Dec 2019 09:24:28 -0500
From:   Qian Cai <cai@....pw>
To:     Eric Auger <eric.auger@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     eric.auger.pro@...il.com, Joerg Roedel <joro@...tes.org>,
        hch@....de, 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 Nov 26, 2019, at 5:27 AM, Eric Auger <eric.auger@...hat.com> 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+


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
>