Messages in this thread | | | Subject | Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit | From | Zhangfei Gao <> | Date | Tue, 26 Apr 2022 13:04:45 +0800 |
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On 2022/4/26 下午12:20, Fenghua Yu wrote: > Hi, Jean and Zhangfei, > > On Mon, Apr 25, 2022 at 05:13:02PM +0100, Jean-Philippe Brucker wrote: >> Could we move mm_pasid_drop() to __mmdrop() instead of __mmput()? For Arm >> we do need to hold the mm_count until unbind(), and mmgrab()/mmdrop() is >> also part of Lu's rework [1]. > Is this a right fix for the issue? Could you please test it on ARM? > I don't have an ARM machine. > > Thanks. > > -Fenghua > > From 84aa68f6174439d863c40cdc2db0e1b89d620dd0 Mon Sep 17 00:00:00 2001 > From: Fenghua Yu <fenghua.yu@intel.com> > Date: Fri, 15 Apr 2022 00:51:33 -0700 > Subject: [PATCH] iommu/sva: Fix PASID use-after-free issue > > A PASID might be still used on ARM after it is freed in __mmput(). > > process: > open()->sva_bind()->ioasid_alloc() = N; // Get PASID N for the mm > exit(); > exit_mm()->__mmput()->mm_pasid_drop()->mm->pasid = -1; // PASID -1 > exit_files()->release(dev)->sva_unbind()->use mm->pasid; // Failure > > To avoid the use-after-free issue, free the PASID after no device uses it, > i.e. after all devices are unbound from the mm. > > sva_bind()/sva_unbind() call mmgrab()/mmdrop() to track mm->mm_count. > __mmdrop() is called only after mm->mm_count is zero. So freeing the PASID > in __mmdrop() guarantees the PASID is safely freed only after no device > is bound to the mm. > > Fixes: 701fac40384f ("iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit") > > Reported-by: Zhangfei Gao <zhangfei.gao@foxmail.com> > Suggested-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > Suggested-by: Jacob Pan <jacob.jun.pan@linux.intel.com> > Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Thanks for the fix.
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
> --- > kernel/fork.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 9796897560ab..35a3beff140b 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -792,6 +792,7 @@ void __mmdrop(struct mm_struct *mm) > mmu_notifier_subscriptions_destroy(mm); > check_mm(mm); > put_user_ns(mm->user_ns); > + mm_pasid_drop(mm); > free_mm(mm); > } > EXPORT_SYMBOL_GPL(__mmdrop); > @@ -1190,7 +1191,6 @@ static inline void __mmput(struct mm_struct *mm) > } > if (mm->binfmt) > module_put(mm->binfmt->module); > - mm_pasid_drop(mm); > mmdrop(mm); > } >
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