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Date: Fri, 15 Apr 2022 18:14:09 +0800 From: "zhangfei.gao@...mail.com" <zhangfei.gao@...mail.com> To: Fenghua Yu <fenghua.yu@...el.com> Cc: Dave Hansen <dave.hansen@...el.com>, Joerg Roedel <joro@...tes.org>, jean-philippe <jean-philippe@...aro.org>, Ravi V Shankar <ravi.v.shankar@...el.com>, Tony Luck <tony.luck@...el.com>, Ashok Raj <ashok.raj@...el.com>, Peter Zijlstra <peterz@...radead.org>, Dave Hansen <dave.hansen@...ux.intel.com>, x86 <x86@...nel.org>, linux-kernel <linux-kernel@...r.kernel.org>, iommu <iommu@...ts.linux-foundation.org>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>, Josh Poimboeuf <jpoimboe@...hat.com>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit On 2022/4/15 下午5:51, Fenghua Yu wrote: > On Thu, Apr 14, 2022 at 06:08:09PM +0800, zhangfei.gao@...mail.com wrote: >> On 2022/4/12 下午11:35, zhangfei.gao@...mail.com wrote: >>> Hi, Fenghua >>> >>> On 2022/4/12 下午9:41, Fenghua Yu wrote: >>>> Hi, Zhangfei, >>>> >>>> On Tue, Apr 12, 2022 at 03:04:09PM +0800, zhangfei.gao@...mail.com >>>> wrote: >>>>> On 2022/4/11 下午10:52, Dave Hansen wrote: >>>>>> On 4/11/22 07:44, zhangfei.gao@...mail.com wrote: >>>>>>> On 2022/4/11 下午10:36, Dave Hansen wrote: >>>>>>>> On 4/11/22 07:20, zhangfei.gao@...mail.com wrote: >>> Agree with Dave, I think user space should not be broken. >>> >>> Thanks >> Any plan about this regression? >> Currently I need this patch to workaround the issue. >> >> 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..2d74ac53d11c 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 >> @@ -4,6 +4,7 @@ >> */ >> >> #include <linux/mm.h> >> +#include <linux/sched/mm.h> >> #include <linux/mmu_context.h> >> #include <linux/mmu_notifier.h> >> #include <linux/slab.h> >> @@ -363,6 +364,7 @@ arm_smmu_sva_bind(struct device *dev, struct mm_struct >> *mm, void *drvdata) >> >> mutex_lock(&sva_lock); >> handle = __arm_smmu_sva_bind(dev, mm); >> + mmget(mm); >> mutex_unlock(&sva_lock); >> return handle; >> } >> @@ -377,6 +379,7 @@ void arm_smmu_sva_unbind(struct iommu_sva *handle) >> arm_smmu_mmu_notifier_put(bond->smmu_mn); >> kfree(bond); >> } >> + mmput(bond->mm); >> mutex_unlock(&sva_lock); >> } > Could you please review and/or test this patch? It's supposed to fix > the PASID issue on both ARM and X86. > > From a6444e1e5bd8076f5e5c5e950d3192de327f0c9c Mon Sep 17 00:00:00 2001 > From: Fenghua Yu <fenghua.yu@...el.com> > Date: Fri, 15 Apr 2022 00:51:33 -0700 > Subject: [RFC PATCH] iommu/sva: Fix PASID use-after-free issue > > A PASID might be still used even though it is freed on mm exit. > > process A: > sva_bind(); > ioasid_alloc() = N; // Get PASID N for the mm > fork(): // spawn process B > exit(); > ioasid_free(N); > > process B: > device uses PASID N -> failure > sva_unbind(); > > Dave Hansen suggests to take a refcount on the mm whenever binding the > PASID to a device and drop the refcount on unbinding. The mm won't be > dropped if the PASID is still bound to it. > > Fixes: 701fac40384f ("iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit") > > Reported-by: Zhangfei Gao <zhangfei.gao@...mail.com> > Suggested-by: Dave Hansen" <dave.hansen@...ux.intel.com> > Signed-off-by: Fenghua Yu <fenghua.yu@...el.com> > --- > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 6 ++++++ > drivers/iommu/intel/svm.c | 4 ++++ > 2 files changed, 10 insertions(+) > > 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..3fcb842a0df0 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 > @@ -7,6 +7,7 @@ > #include <linux/mmu_context.h> > #include <linux/mmu_notifier.h> > #include <linux/slab.h> > +#include <linux/sched/mm.h> > > #include "arm-smmu-v3.h" > #include "../../iommu-sva-lib.h" > @@ -363,6 +364,9 @@ arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm, void *drvdata) > > mutex_lock(&sva_lock); > handle = __arm_smmu_sva_bind(dev, mm); > + /* Take an mm refcount on a successful bind. */ > + if (!IS_ERR(handle)) > + mmget(mm); > mutex_unlock(&sva_lock); > return handle; > } > @@ -372,6 +376,8 @@ void arm_smmu_sva_unbind(struct iommu_sva *handle) > struct arm_smmu_bond *bond = sva_to_bond(handle); > > mutex_lock(&sva_lock); > + /* Drop an mm refcount. */ > + mmput(bond->mm); > if (refcount_dec_and_test(&bond->refs)) { > list_del(&bond->list); > arm_smmu_mmu_notifier_put(bond->smmu_mn); > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c > index 23a38763c1d1..345a0d5d7922 100644 > --- a/drivers/iommu/intel/svm.c > +++ b/drivers/iommu/intel/svm.c > @@ -403,6 +403,8 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu, > goto free_sdev; > > list_add_rcu(&sdev->list, &svm->devs); > + /* Take an mm refcount on binding mm. */ > + mmget(mm); > success: > return &sdev->sva; > > @@ -465,6 +467,8 @@ static int intel_svm_unbind_mm(struct device *dev, u32 pasid) > kfree(svm); > } > } > + /* Drop an mm reference on unbinding mm. */ > + mmput(mm); > } > out: > return ret; This patch can not be applied on 5.18-rc2 for intel part. It should work for arm. In fact I have a similar patch at hand but pending since I found an issue. I start & stop nginx via this cmd. //start sudo sbin/nginx // this alloc an ioasid=1 //stop sudo sbin/nginx -s quit // this does not free ioasid=1, but still alloc ioasid=2. So ioasid will keep allocated but not freed if continue start/stop nginx, though not impact the nginx function. stop nginx with -s quit still calls src/core/nginx.c main -> ngx_ssl_init -> openssl engine: bind_fn -> ... -> alloc asid But openssl engine: ENGINE_free is not called Still in checking nginx code. Or do you test with nginx? Thanks
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