From: Fenghua Yu <fenghua.yu@intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Tony Luck <tony.luck@intel.com>, Ashok Raj <ashok.raj@intel.com>,
Ravi V Shankar <ravi.v.shankar@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
robin.murphy@arm.com, 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>,
zhangfei.gao@linaro.org, Thomas Gleixner <tglx@linutronix.de>,
will@kernel.org
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit
Date: Thu, 28 Apr 2022 08:28:41 -0700 [thread overview]
Message-ID: <YmqyeBfCuDXAMDlZ@fyu1.sc.intel.com> (raw)
In-Reply-To: <bc18351c-27f2-17ae-e781-6b60fbb72541@intel.com>
Hi, Dave,
On Thu, Apr 28, 2022 at 08:09:04AM -0700, Dave Hansen wrote:
> On 4/25/22 21:20, Fenghua Yu wrote:
> >>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().
>
> Is it really just ARM?
Actually it should happen on X86 as well. I will remove "on ARM" in the
changelog.
>
> > 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.
>
> Does this changelog work for everyone?
>
> ==
>
> tl;dr: The PASID is being freed too early. It needs to stay around
> until after device drivers that might be using it have had a chance to
> clear it out of the hardware.
>
Do you want me to change the changlog to add both this paragraph and the
following paragraph?
> --
>
> As a reminder:
>
> mmget() /mmput() refcount the mm's address space
> mmgrab()/mmdrop() refcount the mm itself
>
> The PASID is currently tied to the life of the mm's address space and
> freed in __mmput(). This makes logical sense because the PASID can't be
> used once the address space is gone.
>
> But, this misses an important point: even after the address space is
> gone, the PASID will still be programmed into a device. Device drivers
> might, for instance, still need to flush operations that are outstanding
> and need to use that PASID. They do this at ->release() time.
>
> Device drivers hold a reference on the mm itself and drop it at
> ->release() time. But, the device driver holds a reference mm itself,
> not the address space. The address space (and the PASID) is long gone
> by the time the driver tries to clean up. This is effectively a
> use-after-free bug on the PASID.
>
> To fix this, move the PASID free operation from __mmput() to __mmdrop().
> This ensures that the device drivers' existing mmgrab() keeps the PASID
> allocated until they drop their mm reference.
>
Thank you very much!
-Fenghua
next prev parent reply other threads:[~2022-04-28 15:28 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 23:02 [PATCH v4 00/11] Re-enable ENQCMD and PASID MSR Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 01/11] iommu/sva: Rename CONFIG_IOMMU_SVA_LIB to CONFIG_IOMMU_SVA Fenghua Yu
2022-02-08 2:39 ` Lu Baolu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 02/11] mm: Change CONFIG option for mm->pasid field Fenghua Yu
2022-02-08 2:40 ` Lu Baolu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 03/11] iommu/ioasid: Introduce a helper to check for valid PASIDs Fenghua Yu
2022-02-08 2:40 ` Lu Baolu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 04/11] kernel/fork: Initialize mm's PASID Fenghua Yu
2022-02-14 17:23 ` Thomas Gleixner
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit Fenghua Yu
2022-02-08 2:41 ` Lu Baolu
2022-02-08 15:01 ` Fenghua Yu
2022-02-10 3:16 ` Jacob Pan
2022-02-10 16:27 ` Fenghua Yu
2022-02-10 17:24 ` Luck, Tony
2022-02-10 18:31 ` Fenghua Yu
2022-02-10 23:52 ` Fenghua Yu
2022-02-10 18:49 ` Jacob Pan
2022-02-10 23:15 ` Fenghua Yu
2022-02-11 22:00 ` Dave Hansen
2022-02-14 17:24 ` Thomas Gleixner
2022-02-15 9:55 ` Joerg Roedel
[not found] ` <tencent_F6830A1196DB4C6A904D7C691F0D961D1108@qq.com>
2022-04-11 14:10 ` Dave Hansen
2022-04-11 14:20 ` zhangfei.gao
2022-04-11 14:36 ` Dave Hansen
2022-04-11 14:44 ` zhangfei.gao
2022-04-11 14:52 ` Dave Hansen
2022-04-11 15:13 ` zhangfei.gao
2022-04-12 7:04 ` zhangfei.gao
2022-04-12 13:41 ` Fenghua Yu
2022-04-12 14:39 ` Dave Hansen
2022-04-15 9:59 ` Fenghua Yu
2022-04-12 15:35 ` zhangfei.gao
2022-04-14 10:08 ` zhangfei.gao
2022-04-15 9:51 ` Fenghua Yu
[not found] ` <99bcb9f5-4776-9c40-a776-cdecfa9e1010@foxmail.com>
2022-04-15 10:14 ` zhangfei.gao
2022-04-15 10:50 ` Fenghua Yu
2022-04-15 11:52 ` zhangfei.gao
2022-04-15 12:37 ` Fenghua Yu
2022-04-16 1:30 ` zhangfei.gao
2022-04-15 19:07 ` Fenghua Yu
2022-04-15 21:00 ` Jacob Pan
2022-04-16 1:43 ` zhangfei.gao
2022-04-18 18:14 ` Jacob Pan
2022-04-19 1:02 ` zhangfei.gao
2022-04-18 6:34 ` Tian, Kevin
2022-04-18 18:11 ` Jacob Pan
2022-04-20 16:45 ` Jean-Philippe Brucker
2022-04-21 6:47 ` zhangfei.gao
2022-04-22 9:03 ` zhangfei.gao
2022-04-22 10:11 ` Jean-Philippe Brucker
2022-04-22 13:15 ` zhangfei.gao
2022-04-22 15:50 ` Jean-Philippe Brucker
2022-04-23 11:13 ` zhangfei.gao
2022-04-24 2:58 ` Zhangfei Gao
2022-04-24 9:52 ` Zhangfei Gao
2022-04-25 13:53 ` Jean-Philippe Brucker
2022-04-25 14:18 ` Dave Hansen
2022-04-25 14:26 ` Jean-Philippe Brucker
2022-04-25 15:34 ` Jacob Pan
2022-04-25 16:13 ` Jean-Philippe Brucker
2022-04-25 22:32 ` Jacob Pan
2022-04-26 4:20 ` Fenghua Yu
2022-04-26 5:04 ` Zhangfei Gao
2022-04-28 0:54 ` Fenghua Yu
2022-04-28 8:43 ` Jean-Philippe Brucker
2022-04-28 15:09 ` Dave Hansen
2022-04-28 15:28 ` Fenghua Yu [this message]
2022-04-28 15:42 ` Dave Hansen
2022-04-28 16:01 ` Jean-Philippe Brucker
2022-04-28 16:35 ` Dave Hansen
2022-04-26 4:28 ` Zhangfei Gao
2022-04-26 4:36 ` Fenghua Yu
2022-04-26 5:19 ` Zhangfei Gao
2022-04-25 15:55 ` Dave Hansen
2022-04-25 16:40 ` Jean-Philippe Brucker
2022-04-26 15:27 ` Dave Hansen
2022-04-26 16:48 ` Jean-Philippe Brucker
2022-04-26 23:31 ` Dave Hansen
2022-04-28 8:39 ` Jean-Philippe Brucker
2022-04-29 7:53 ` Baolu Lu
2022-04-29 13:51 ` Fenghua Yu
2022-04-29 14:34 ` Jean-Philippe Brucker
2022-04-29 22:19 ` Fenghua Yu
2022-04-30 7:33 ` Baolu Lu
2022-05-03 7:49 ` Jean-Philippe Brucker
2022-05-06 5:36 ` Baolu Lu
2022-04-12 14:36 ` Dave Hansen
2022-04-12 15:10 ` Jean-Philippe Brucker
2022-04-12 15:35 ` Dave Hansen
2022-04-13 11:14 ` Lu Baolu
2022-04-25 2:57 ` zhangfei.gao
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 06/11] x86/fpu: Clear PASID when copying fpstate Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 07/11] sched: Define and initialize a flag to identify valid PASID in the task Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Peter Zijlstra
2022-02-07 23:02 ` [PATCH v4 08/11] x86/traps: Demand-populate PASID MSR via #GP Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 09/11] x86/cpufeatures: Re-enable ENQCMD Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 10/11] tools/objtool: Check for use of the ENQCMD instruction in the kernel Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-03-09 7:55 ` [tip: x86/core] " tip-bot2 for Fenghua Yu
2022-03-15 10:44 ` tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 11/11] docs: x86: Change documentation for SVA (Shared Virtual Addressing) Fenghua Yu
2022-02-14 17:25 ` Thomas Gleixner
2022-02-15 10:54 ` [tip: x86/pasid] Documentation/x86: Update " tip-bot2 for Fenghua Yu
2022-02-11 20:04 ` [PATCH v4 00/11] Re-enable ENQCMD and PASID MSR Fenghua Yu
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