[PATCH v2] iommu/arm-smmu-v3-sva: Fix mm use-after-free

[PATCH v2] iommu/arm-smmu-v3-sva: Fix mm use-after-free

[Jean-Philippe Brucker]

We currently call arm64_mm_context_put() without holding a reference to
the mm, which can result in use-after-free. Call mmgrab()/mmdrop() to
ensure the mm only gets freed after we unpinned the ASID.

Fixes: 32784a9562fb ("iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
v2: Add missing include
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index 22ddd05bbdcd..5d029e87c8af 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -6,6 +6,7 @@
 #include <linux/mm.h>
 #include <linux/mmu_context.h>
 #include <linux/mmu_notifier.h>
+#include <linux/sched/mm.h>
 #include <linux/slab.h>
 
 #include "arm-smmu-v3.h"
@@ -96,9 +97,14 @@ static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
 	struct arm_smmu_ctx_desc *cd;
 	struct arm_smmu_ctx_desc *ret = NULL;
 
+	/* Don't free the mm until we release the ASID */
+	mmgrab(mm);
+
 	asid = arm64_mm_context_get(mm);
-	if (!asid)
-		return ERR_PTR(-ESRCH);
+	if (!asid) {
+		err = -ESRCH;
+		goto out_drop_mm;
+	}
 
 	cd = kzalloc(sizeof(*cd), GFP_KERNEL);
 	if (!cd) {
@@ -165,6 +171,8 @@ static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
 	kfree(cd);
 out_put_context:
 	arm64_mm_context_put(mm);
+out_drop_mm:
+	mmdrop(mm);
 	return err < 0 ? ERR_PTR(err) : ret;
 }
 
@@ -173,6 +181,7 @@ static void arm_smmu_free_shared_cd(struct arm_smmu_ctx_desc *cd)
 	if (arm_smmu_free_asid(cd)) {
 		/* Unpin ASID */
 		arm64_mm_context_put(cd->mm);
+		mmdrop(cd->mm);
 		kfree(cd);
 	}
 }
-- 
2.35.1

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Re: [PATCH v2] iommu/arm-smmu-v3-sva: Fix mm use-after-free

[Zhangfei Gao]

On 2022/4/26 下午9:04, Jean-Philippe Brucker wrote:
> We currently call arm64_mm_context_put() without holding a reference to
> the mm, which can result in use-after-free. Call mmgrab()/mmdrop() to
> ensure the mm only gets freed after we unpinned the ASID.
>
> Fixes: 32784a9562fb ("iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()")
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

Thanks Jean

Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>


> ---
> v2: Add missing include
> ---
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> index 22ddd05bbdcd..5d029e87c8af 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> @@ -6,6 +6,7 @@
>   #include <linux/mm.h>
>   #include <linux/mmu_context.h>
>   #include <linux/mmu_notifier.h>
> +#include <linux/sched/mm.h>
>   #include <linux/slab.h>
>   
>   #include "arm-smmu-v3.h"
> @@ -96,9 +97,14 @@ static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
>   	struct arm_smmu_ctx_desc *cd;
>   	struct arm_smmu_ctx_desc *ret = NULL;
>   
> +	/* Don't free the mm until we release the ASID */
> +	mmgrab(mm);
> +
>   	asid = arm64_mm_context_get(mm);
> -	if (!asid)
> -		return ERR_PTR(-ESRCH);
> +	if (!asid) {
> +		err = -ESRCH;
> +		goto out_drop_mm;
> +	}
>   
>   	cd = kzalloc(sizeof(*cd), GFP_KERNEL);
>   	if (!cd) {
> @@ -165,6 +171,8 @@ static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
>   	kfree(cd);
>   out_put_context:
>   	arm64_mm_context_put(mm);
> +out_drop_mm:
> +	mmdrop(mm);
>   	return err < 0 ? ERR_PTR(err) : ret;
>   }
>   
> @@ -173,6 +181,7 @@ static void arm_smmu_free_shared_cd(struct arm_smmu_ctx_desc *cd)
>   	if (arm_smmu_free_asid(cd)) {
>   		/* Unpin ASID */
>   		arm64_mm_context_put(cd->mm);
> +		mmdrop(cd->mm);
>   		kfree(cd);
>   	}
>   }

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Re: [PATCH v2] iommu/arm-smmu-v3-sva: Fix mm use-after-free

[Will Deacon]

On Tue, 26 Apr 2022 14:04:45 +0100, Jean-Philippe Brucker wrote:
> We currently call arm64_mm_context_put() without holding a reference to
> the mm, which can result in use-after-free. Call mmgrab()/mmdrop() to
> ensure the mm only gets freed after we unpinned the ASID.
> 
> 

Applied to will (for-joerg/arm-smmu/updates), thanks!

[1/1] iommu/arm-smmu-v3-sva: Fix mm use-after-free
      https://git.kernel.org/will/c/cbd23144f766

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
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