This is a note to let you know that I've just added the patch titled iommu/arm-smmu-v3-sva: Fix mm use-after-free to the 5.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: iommu-arm-smmu-v3-sva-fix-mm-use-after-free.patch and it can be found in the queue-5.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 08b43736f88edd2a180463f2bdafb66bc6ba4a81 Author: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> Date: Tue Apr 26 14:04:45 2022 +0100 iommu/arm-smmu-v3-sva: Fix mm use-after-free [ Upstream commit cbd23144f7662b00bcde32a938c4a4057e476d68 ] 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@xxxxxxxxxx> Tested-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220426130444.300556-1-jean-philippe@xxxxxxxxxx Signed-off-by: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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 c623dae1e115..1ef7bbb4acf3 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); } }