diff mbox series

答复: [External Mail][PATCH-tip] sched: Fix use-after-free bug in dup_user_cpus_ptr()

Message ID 63373bf9adfc4e0abd9480d40afa2c5a@xiaomi.com
State New
Headers
Series 答复: [External Mail][PATCH-tip] sched: Fix use-after-free bug in dup_user_cpus_ptr() |

Commit Message

David Wang 王标 Nov. 28, 2022, 1:34 p.m. UTC 
  Hi, Waiman

We use 140 devices to test this patch 72 hours.  The issue can not be reproduced.  If no this patch,  the issue can be reproduced.
Could you help merge this patch to mailine?

https://lore.kernel.org/all/20221125023943.1118603-1-longman@redhat.com/

If this patch is applied to the maintainer's tree,  we can request google to help cherrypick to ACK to fix issue.

Thanks

-----邮件原件-----
发件人: Waiman Long <longman@redhat.com>
发送时间: 2022年11月28日 9:45
收件人: Ingo Molnar <mingo@redhat.com>; Peter Zijlstra <peterz@infradead.org>; Juri Lelli <juri.lelli@redhat.com>; Vincent Guittot <vincent.guittot@linaro.org>; Dietmar Eggemann <dietmar.eggemann@arm.com>; Steven Rostedt <rostedt@goodmis.org>; Ben Segall <bsegall@google.com>; Mel Gorman <mgorman@suse.de>; Daniel Bristot de Oliveira <bristot@redhat.com>
抄送: Phil Auld <pauld@redhat.com>; Wenjie Li <wenjieli@qti.qualcomm.com>; David Wang 王标 <wangbiao3@xiaomi.com>; linux-kernel@vger.kernel.org; Waiman Long <longman@redhat.com>; stable@vger.kernel.org
主题: [External Mail][PATCH-tip] sched: Fix use-after-free bug in dup_user_cpus_ptr()

[外部邮件] 此邮件来源于小米公司外部，请谨慎处理。若对邮件安全性存疑，请将邮件转发给misec@xiaomi.com进行反馈

Since commit 07ec77a1d4e8 ("sched: Allow task CPU affinity to be restricted on asymmetric systems"), the setting and clearing of user_cpus_ptr are done under pi_lock for arm64 architecture. However,
dup_user_cpus_ptr() accesses user_cpus_ptr without any lock protection. When racing with the clearing of user_cpus_ptr in __set_cpus_allowed_ptr_locked(), it can lead to user-after-free and double-free in arm64 kernel.

Commit 8f9ea86fdf99 ("sched: Always preserve the user requested
cpumask") fixes this problem as user_cpus_ptr, once set, will never be cleared in a task's lifetime. However, this bug was re-introduced in commit 851a723e45d1 ("sched: Always clear user_cpus_ptr in
do_set_cpus_allowed()") which allows the clearing of user_cpus_ptr in do_set_cpus_allowed(). This time, it will affect all arches.

Fix this bug by always clearing the user_cpus_ptr of the newly cloned/forked task before the copying process starts and check the user_cpus_ptr state of the source task under pi_lock.

Note to stable, this patch won't be applicable to stable releases.
Just copy the new dup_user_cpus_ptr() function over.

Fixes: 07ec77a1d4e8 ("sched: Allow task CPU affinity to be restricted on asymmetric systems")
Fixes: 851a723e45d1 ("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()")
CC: stable@vger.kernel.org
Reported-by: David Wang 王标 <wangbiao3@xiaomi.com>
Signed-off-by: Waiman Long <longman@redhat.com>
---
 kernel/sched/core.c | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)


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Comments

Waiman Long Nov. 28, 2022, 3:43 p.m. UTC | #1 
On 11/28/22 08:34, David Wang 王标 wrote:
> Hi, Waiman
>
> We use 140 devices to test this patch 72 hours.  The issue can not be reproduced.  If no this patch,  the issue can be reproduced.
> Could you help merge this patch to mailine?
>
> https://lore.kernel.org/all/20221125023943.1118603-1-longman@redhat.com/
>
> If this patch is applied to the maintainer's tree,  we can request google to help cherrypick to ACK to fix issue.

Just want to clarify if you are testing the patch using the latest tip 
tree or on top of an existing linux version without the persistent user 
requested affinity patchset.

PeterZ is the scheduler maintainer who is responsible for merging 
scheduler related patch. It is up to him as to when that will happen.

Cheers,
Longman
David Wang 王标 Nov. 29, 2022, 3:11 a.m. UTC | #2 
Hi  Waiman,  Peterz,

We test new patch basing on user requested affinity patchset(the latest tip tree).

You use 7 patch from ACK code . You check following  link change.
https://android-review.googlesource.com/c/kernel/common/+/2266724
https://android-review.googlesource.com/c/kernel/common/+/2266744
https://android-review.googlesource.com/c/kernel/common/+/2266745
https://android-review.googlesource.com/c/kernel/common/+/2266804
https://android-review.googlesource.com/c/kernel/common/+/2266784
https://android-review.googlesource.com/c/kernel/common/+/2267468
https://android-review.googlesource.com/c/kernel/common/+/2267664

You can confirm this with google team and check
https://partnerissuetracker.corp.google.com/u/0/issues/256578302 .

Hi  Peterz ,

Could you help merge
https://lore.kernel.org/all/20221125023943.1118603-1-longman@redhat.com/

We want to provide better product for user.
Thanks

David.

-----邮件原件-----
发件人: Waiman Long <longman@redhat.com>
发送时间: 2022年11月28日 23:43
收件人: David Wang 王标 <wangbiao3@xiaomi.com>; Ingo Molnar <mingo@redhat.com>; Peter Zijlstra <peterz@infradead.org>; Juri Lelli <juri.lelli@redhat.com>; Vincent Guittot <vincent.guittot@linaro.org>; Dietmar Eggemann <dietmar.eggemann@arm.com>; Steven Rostedt <rostedt@goodmis.org>; Ben Segall <bsegall@google.com>; Mel Gorman <mgorman@suse.de>; Daniel Bristot de Oliveira <bristot@redhat.com>
抄送: Phil Auld <pauld@redhat.com>; Wenjie Li <wenjieli@qti.qualcomm.com>; linux-kernel@vger.kernel.org; stable@vger.kernel.org
主题: Re: 答复: [External Mail][PATCH-tip] sched: Fix use-after-free bug in dup_user_cpus_ptr()

[外部邮件] 此邮件来源于小米公司外部，请谨慎处理。若对邮件安全性存疑，请将邮件转发给misec@xiaomi.com进行反馈

On 11/28/22 08:34, David Wang 王标 wrote:
> Hi, Waiman
>
> We use 140 devices to test this patch 72 hours.  The issue can not be reproduced.  If no this patch,  the issue can be reproduced.
> Could you help merge this patch to mailine?
>
> https://lore.kernel.org/all/20221125023943.1118603-1-longman@redhat.co
> m/
>
> If this patch is applied to the maintainer's tree,  we can request google to help cherrypick to ACK to fix issue.

Just want to clarify if you are testing the patch using the latest tip tree or on top of an existing linux version without the persistent user requested affinity patchset.

PeterZ is the scheduler maintainer who is responsible for merging scheduler related patch. It is up to him as to when that will happen.

Cheers,
Longman

#/******本邮件及其附件含有小米公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from XIAOMI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it!******/#
diff mbox series

Patch

diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8df51b08bb38..f2b75faaf71a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2624,19 +2624,43 @@  void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)  int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,
                      int node)
 {
+       cpumask_t *user_mask;
        unsigned long flags;

+       /*
+        * Always clear dst->user_cpus_ptr first as their user_cpus_ptr's
+        * may differ by now due to racing.
+        */
+       dst->user_cpus_ptr = NULL;
+
+       /*
+        * This check is racy and losing the race is a valid situation.
+        * It is not worth the extra overhead of taking the pi_lock on
+        * every fork/clone.
+        */
        if (!src->user_cpus_ptr)
                return 0;

-       dst->user_cpus_ptr = kmalloc_node(cpumask_size(), GFP_KERNEL, node);
-       if (!dst->user_cpus_ptr)
+       user_mask = kmalloc_node(cpumask_size(), GFP_KERNEL, node);
+       if (!user_mask)
                return -ENOMEM;

-       /* Use pi_lock to protect content of user_cpus_ptr */
+       /*
+        * Use pi_lock to protect content of user_cpus_ptr
+        *
+        * Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent
+        * do_set_cpus_allowed().
+        */
        raw_spin_lock_irqsave(&src->pi_lock, flags);
-       cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);
+       if (src->user_cpus_ptr) {
+               swap(dst->user_cpus_ptr, user_mask);
+               cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);
+       }
        raw_spin_unlock_irqrestore(&src->pi_lock, flags);
+
+       if (unlikely(user_mask))
+               kfree(user_mask);
+
        return 0;
 }

--
2.31.1