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Message-ID: <tencent_76E043C4D1B6A21A5253579A61034107EB06@qq.com>
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID
 allocation and free it on mm exit
To:     Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Fenghua Yu <fenghua.yu@intel.com>
Cc:     Dave Hansen <dave.hansen@intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        Ravi V Shankar <ravi.v.shankar@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        x86 <x86@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        iommu <iommu@lists.linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, will@kernel.org,
        robin.murphy@arm.com
References: <56ed509d-a7cf-1fde-676c-a28eb204989b@intel.com>
 <tencent_9920B633D50E9B80D3A41A723BCE06972309@qq.com>
 <f439dde5-0eaa-52e4-9cf7-2ed1f62ea07f@intel.com>
 <tencent_F73C11A7DBAC6AF24D3369DF0DCA1D7E8308@qq.com>
 <a139dbad-2f42-913b-677c-ef35f1eebfed@intel.com>
 <tencent_B683AC1146DB6A6ABB4D73697C0D6A1D7608@qq.com>
 <YlWBkyGeb2ZOGLKl@fyu1.sc.intel.com>
 <tencent_A9458C6CEBAADD361DA765356477B00E920A@qq.com>
 <tencent_8B6D7835F62688B4CD069C0EFC41B308B407@qq.com>
 <YllADL6uMoLllzQo@fyu1.sc.intel.com> <YmA4pbgevqln/jSO@myrica>
From:   "zhangfei.gao@foxmail.com" <zhangfei.gao@foxmail.com>
Date:   Thu, 21 Apr 2022 14:47:23 +0800
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On 2022/4/21 上午12:45, Jean-Philippe Brucker wrote:
> Hi,
>
> On Fri, Apr 15, 2022 at 02:51:08AM -0700, Fenghua Yu wrote:
>>  From a6444e1e5bd8076f5e5c5e950d3192de327f0c9c Mon Sep 17 00:00:00 2001
>> From: Fenghua Yu <fenghua.yu@intel.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@foxmail.com>
>> Suggested-by: Dave Hansen" <dave.hansen@linux.intel.com>
>> Signed-off-by: Fenghua Yu <fenghua.yu@intel.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);
> I do like the idea because it will simplify the driver. We can't call
> mmput() here, though, because it may call the release() MMU notifier which
> will try to grab sva_lock, already held.
>
> I also found another use-after-free in arm_smmu_free_shared_cd(), where we
> call arm64_mm_context_put() when the mm could already be freed. There used
> to be an mmgrab() preventing this but it went away during a rewrite.
>
> To fix both we could just move mmput() at the end of unbind() but I'd
> rather do a proper cleanup removing the release() notifier right away.
> Zhangfei, could you try the patch below?
>
> Thanks,
> Jean
>
> --- 8< ---
>
>  From 4e09c0d71dfb35fc90915bd1e36545027fbf8a03 Mon Sep 17 00:00:00 2001
> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Date: Wed, 20 Apr 2022 10:19:24 +0100
> Subject: [PATCH] iommu/arm-smmu-v3-sva: Fix PASID and mm use-after-free issues
>
> Commit 701fac40384f ("iommu/sva: Assign a PASID to mm on PASID
> allocation and free it on mm exit") frees the PASID earlier than what
> the SMMUv3 driver expects. At the moment the SMMU driver handles mm exit
> in the release() MMU notifier by quiescing the context descriptor. The
> context descriptor is only made invalid in unbind(), after the device
> driver ensured the PASID is not used anymore. Releasing the PASID on mm
> exit may cause it to be reallocated while it is still used by the
> context descriptor.
>
> There is another use-after-free, present since the beginning, where we
> call arm64_mm_context_put() without a guarantee that mm_count is held.
>
> Dave Hansen suggests to grab mm_users whenever binding the mm to a
> device and drop it on unbinding. With that we can fix both issues and
> simplify the driver by removing the release() notifier.
>
> Fixes: 32784a9562fb ("iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()")
> Reported-by: Zhangfei Gao <zhangfei.gao@foxmail.com>
> Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  1 -
>   .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   | 49 +++++--------------
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 14 +-----
>   3 files changed, 15 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index cd48590ada30..d50d215d946c 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -735,7 +735,6 @@ static inline struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
>   
>   extern struct xarray arm_smmu_asid_xa;
>   extern struct mutex arm_smmu_asid_lock;
> -extern struct arm_smmu_ctx_desc quiet_cd;
>   
>   int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, int ssid,
>   			    struct arm_smmu_ctx_desc *cd);
> 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..f9dff0f6cdd4 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"
> @@ -15,7 +16,6 @@
>   struct arm_smmu_mmu_notifier {
>   	struct mmu_notifier		mn;
>   	struct arm_smmu_ctx_desc	*cd;
> -	bool				cleared;
>   	refcount_t			refs;
>   	struct list_head		list;
>   	struct arm_smmu_domain		*domain;
> @@ -96,9 +96,14 @@ 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;
>   
> +	/* Prevent mm exit as long as it is used by the context descriptor */
> +	mmget(mm);
> +
>   	asid = arm64_mm_context_get(mm);
> -	if (!asid)
> -		return ERR_PTR(-ESRCH);
> +	if (!asid) {
> +		err = -ESRCH;
> +		goto out_put_mm;
> +	}
>   
>   	cd = kzalloc(sizeof(*cd), GFP_KERNEL);
>   	if (!cd) {
> @@ -165,6 +170,8 @@ 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_put_mm:
> +	mmput(mm);
>   	return err < 0 ? ERR_PTR(err) : ret;
>   }
>   
> @@ -173,6 +180,7 @@ 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);
> +		mmput(cd->mm);
>   		kfree(cd);
>   	}
>   }
> @@ -191,30 +199,6 @@ static void arm_smmu_mm_invalidate_range(struct mmu_notifier *mn,
>   	arm_smmu_atc_inv_domain(smmu_domain, mm->pasid, start, size);
>   }
>   
> -static void arm_smmu_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
> -{
> -	struct arm_smmu_mmu_notifier *smmu_mn = mn_to_smmu(mn);
> -	struct arm_smmu_domain *smmu_domain = smmu_mn->domain;
> -
> -	mutex_lock(&sva_lock);
> -	if (smmu_mn->cleared) {
> -		mutex_unlock(&sva_lock);
> -		return;
> -	}
> -
> -	/*
> -	 * DMA may still be running. Keep the cd valid to avoid C_BAD_CD events,
> -	 * but disable translation.
> -	 */
> -	arm_smmu_write_ctx_desc(smmu_domain, mm->pasid, &quiet_cd);
> -
> -	arm_smmu_tlb_inv_asid(smmu_domain->smmu, smmu_mn->cd->asid);
> -	arm_smmu_atc_inv_domain(smmu_domain, mm->pasid, 0, 0);
> -
> -	smmu_mn->cleared = true;
> -	mutex_unlock(&sva_lock);
> -}
> -
>   static void arm_smmu_mmu_notifier_free(struct mmu_notifier *mn)
>   {
>   	kfree(mn_to_smmu(mn));
> @@ -222,7 +206,6 @@ static void arm_smmu_mmu_notifier_free(struct mmu_notifier *mn)
>   
>   static const struct mmu_notifier_ops arm_smmu_mmu_notifier_ops = {
>   	.invalidate_range	= arm_smmu_mm_invalidate_range,
> -	.release		= arm_smmu_mm_release,
>   	.free_notifier		= arm_smmu_mmu_notifier_free,
>   };
>   
> @@ -290,14 +273,8 @@ static void arm_smmu_mmu_notifier_put(struct arm_smmu_mmu_notifier *smmu_mn)
>   	list_del(&smmu_mn->list);
>   	arm_smmu_write_ctx_desc(smmu_domain, mm->pasid, NULL);
>   
> -	/*
> -	 * If we went through clear(), we've already invalidated, and no
> -	 * new TLB entry can have been formed.
> -	 */
> -	if (!smmu_mn->cleared) {
> -		arm_smmu_tlb_inv_asid(smmu_domain->smmu, cd->asid);
> -		arm_smmu_atc_inv_domain(smmu_domain, mm->pasid, 0, 0);
> -	}
> +	arm_smmu_tlb_inv_asid(smmu_domain->smmu, cd->asid);
> +	arm_smmu_atc_inv_domain(smmu_domain, mm->pasid, 0, 0);
>   
>   	/* Frees smmu_mn */
>   	mmu_notifier_put(&smmu_mn->mn);
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 627a3ed5ee8f..246670318eda 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -76,12 +76,6 @@ struct arm_smmu_option_prop {
>   DEFINE_XARRAY_ALLOC1(arm_smmu_asid_xa);
>   DEFINE_MUTEX(arm_smmu_asid_lock);
>   
> -/*
> - * Special value used by SVA when a process dies, to quiesce a CD without
> - * disabling it.
> - */
> -struct arm_smmu_ctx_desc quiet_cd = { 0 };
> -
>   static struct arm_smmu_option_prop arm_smmu_options[] = {
>   	{ ARM_SMMU_OPT_SKIP_PREFETCH, "hisilicon,broken-prefetch-cmd" },
>   	{ ARM_SMMU_OPT_PAGE0_REGS_ONLY, "cavium,cn9900-broken-page1-regspace"},
> @@ -1047,9 +1041,7 @@ int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, int ssid,
>   	 * (2) Install a secondary CD, for SID+SSID traffic.
>   	 * (3) Update ASID of a CD. Atomically write the first 64 bits of the
>   	 *     CD, then invalidate the old entry and mappings.
> -	 * (4) Quiesce the context without clearing the valid bit. Disable
> -	 *     translation, and ignore any translation fault.
> -	 * (5) Remove a secondary CD.
> +	 * (4) Remove a secondary CD.
>   	 */
>   	u64 val;
>   	bool cd_live;
> @@ -1065,10 +1057,8 @@ int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, int ssid,
>   	val = le64_to_cpu(cdptr[0]);
>   	cd_live = !!(val & CTXDESC_CD_0_V);
>   
> -	if (!cd) { /* (5) */
> +	if (!cd) { /* (4) */
>   		val = 0;
> -	} else if (cd == &quiet_cd) { /* (4) */
> -		val |= CTXDESC_CD_0_TCR_EPD0;
>   	} else if (cd_live) { /* (3) */
>   		val &= ~CTXDESC_CD_0_ASID;
>   		val |= FIELD_PREP(CTXDESC_CD_0_ASID, cd->asid);
Thanks Jean

Have tested, still got some issue with our openssl-engine.

1. If openssl-engine does not register rsa, nginx works well.

2. If openssl-engine register rsa, nginx also works, but ioasid is not 
freed when nginx stop.

IMPLEMENT_DYNAMIC_BIND_FN(bind_fn)
bind_fn
ENGINE_set_RSA(e, rsa_methods())

destroy_fn

If ENGINE_set_RSA is set, nginx start and stop will NOT call destroy_fn.
Even rsa_methods is almost new via RSA_meth_new.

In 5.18-rcx, this caused ioasid  not freed in nginx start and stop.
In 5.17, though destroy_fn is not called, but ioasid is freed when nginx 
stop, so not noticed this issue before.

Still in checking why ENGINE_set_RSA blocks destroy_fn.

Thanks