Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit
From: zhangfei.gao@xxxxxxxxxxx
Date: Fri Apr 15 2022 - 07:53:49 EST
On 2022/4/15 下午6:50, Fenghua Yu wrote:
Hi, Zhangfei,
On Fri, Apr 15, 2022 at 06:14:09PM +0800, zhangfei.gao@xxxxxxxxxxx wrote:
On 2022/4/15 下午5:51, Fenghua Yu wrote:
On Thu, Apr 14, 2022 at 06:08:09PM +0800, zhangfei.gao@xxxxxxxxxxx wrote:
On 2022/4/12 下午11:35, zhangfei.gao@xxxxxxxxxxx wrote:
Hi, Fenghua
On 2022/4/12 下午9:41, Fenghua Yu wrote:
From a6444e1e5bd8076f5e5c5e950d3192de327f0c9c Mon Sep 17 00:00:00 2001
From: Fenghua Yu <fenghua.yu@xxxxxxxxx>
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@xxxxxxxxxxx>
Suggested-by: Dave Hansen" <dave.hansen@xxxxxxxxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
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.
What error do you see? Could you please send to me errors?
I download this patch from:
https://lore.kernel.org/lkml/YllADL6uMoLllzQo@xxxxxxxxxxxxxxxxx/raw
git am to either v5.18-rc2 or the latest upstream without any issue.
It is my copy paste issue.
I have tested, nginx woks well.
Other than the following issue,
Each time /sbin/nginx will alloc ioasid but not free.
which I think it maybe nginx issue or the mis-usage, will ask there.
Tested-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
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?
On my X86 machine, nginx doesn't trigger the kernel sva binding function
to allocate ioasid. I tried pre- nstalled nginx/openssl and also tried my built
a few versions of nginx/openssl. nginx does call OPENSSL_init_ssl() but
doesn't go to the binding function. Don't know if it's my configuration issue.
Maybe you can give me some advice?
I am using openssl engine, which use crypto driver and using sva via uacce.
nginx -> openssl -> openssl engine -> sva related.
I test the patch with a few internal test tools and observe mmget()/mmput()
works fine in various cases.
OK, thanks