[PATCH] mm,hwpoison: check mm when killing accessing process

[PATCH] mm,hwpoison: check mm when killing accessing process

[Shuai Xue]

The GHES code calls memory_failure_queue() from IRQ context to queue work
into workqueue and schedule it on the current CPU. Then the work is
processed in memory_failure_work_func() by kworker and calls
memory_failure().

When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
SIGBUS with error virutal address") make memory_failure() call
kill_accessing_process() that:

    - holds mmap locking of current->mm
    - does pagetable walk to find the error virtual address
    - and sends SIGBUS to the current process with error info.

However, the mm of kworker is not valid. Therefore, check mm when killing
accessing process.

Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
---
 mm/memory-failure.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 14439806b5ef..7553917ce820 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -743,6 +743,9 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
 	};
 	priv.tk.tsk = p;
 
+	if (!p->mm)
+		return -EFAULT;
+
 	mmap_read_lock(p->mm);
 	ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwp_walk_ops,
 			      (void *)&priv);
@@ -751,6 +754,7 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
 	else
 		ret = 0;
 	mmap_read_unlock(p->mm);
+
 	return ret > 0 ? -EHWPOISON : -EFAULT;
 }
 
-- 
2.20.1.12.g72788fdb

Re: [PATCH] mm,hwpoison: check mm when killing accessing process

[Andrew Morton]

On Wed, 14 Sep 2022 14:49:35 +0800 Shuai Xue <xueshuai@linux.alibaba.com> wrote:

> The GHES code calls memory_failure_queue() from IRQ context to queue work
> into workqueue and schedule it on the current CPU. Then the work is
> processed in memory_failure_work_func() by kworker and calls
> memory_failure().
> 
> When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
> SIGBUS with error virutal address") make memory_failure() call
> kill_accessing_process() that:
> 
>     - holds mmap locking of current->mm
>     - does pagetable walk to find the error virtual address
>     - and sends SIGBUS to the current process with error info.
> 
> However, the mm of kworker is not valid. Therefore, check mm when killing
> accessing process.

Thanks.

When fixing a bug, please always describe the user-visible effects of
tha bug.  I'm thinking "null pointer deref crashes the kernel".

> Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>

I'll add cc:stable.

> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -743,6 +743,9 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>  	};
>  	priv.tk.tsk = p;
>  
> +	if (!p->mm)
> +		return -EFAULT;
> +
>  	mmap_read_lock(p->mm);
>  	ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwp_walk_ops,
>  			      (void *)&priv);
> @@ -751,6 +754,7 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>  	else
>  		ret = 0;
>  	mmap_read_unlock(p->mm);
> +
>  	return ret > 0 ? -EHWPOISON : -EFAULT;
>  }

This is an unrelated change which doesn't appear to match the style in
memory-failure.c, so I'll drop this hunk.

Re: [PATCH] mm,hwpoison: check mm when killing accessing process

[Shuai Xue]

在 2022/9/15 AM6:35, Andrew Morton 写道:
> On Wed, 14 Sep 2022 14:49:35 +0800 Shuai Xue <xueshuai@linux.alibaba.com> wrote:
> 
>> The GHES code calls memory_failure_queue() from IRQ context to queue work
>> into workqueue and schedule it on the current CPU. Then the work is
>> processed in memory_failure_work_func() by kworker and calls
>> memory_failure().
>>
>> When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
>> SIGBUS with error virutal address") make memory_failure() call
>> kill_accessing_process() that:
>>
>>     - holds mmap locking of current->mm
>>     - does pagetable walk to find the error virtual address
>>     - and sends SIGBUS to the current process with error info.
>>
>> However, the mm of kworker is not valid. Therefore, check mm when killing
>> accessing process.
> 
> Thanks.
> 
> When fixing a bug, please always describe the user-visible effects of
> tha bug.  I'm thinking "null pointer deref crashes the kernel".

Got it. Thank you :)

> 
>> Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
>> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> 
> I'll add cc:stable.

Thanks.

> 
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -743,6 +743,9 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>>  	};
>>  	priv.tk.tsk = p;
>>  
>> +	if (!p->mm)
>> +		return -EFAULT;
>> +
>>  	mmap_read_lock(p->mm);
>>  	ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwp_walk_ops,
>>  			      (void *)&priv);
>> @@ -751,6 +754,7 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>>  	else
>>  		ret = 0;
>>  	mmap_read_unlock(p->mm);
>> +
>>  	return ret > 0 ? -EHWPOISON : -EFAULT;
>>  }
> 
> This is an unrelated change which doesn't appear to match the style in
> memory-failure.c, so I'll drop this hunk.

I see, thanks.

Cheers,
Shuai

Re: [PATCH] mm,hwpoison: check mm when killing accessing process

[Miaohe Lin]

On 2022/9/14 14:49, Shuai Xue wrote:
> The GHES code calls memory_failure_queue() from IRQ context to queue work
> into workqueue and schedule it on the current CPU. Then the work is
> processed in memory_failure_work_func() by kworker and calls
> memory_failure().
> 
> When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
> SIGBUS with error virutal address") make memory_failure() call
> kill_accessing_process() that:
> 
>     - holds mmap locking of current->mm
>     - does pagetable walk to find the error virtual address
>     - and sends SIGBUS to the current process with error info.
> 
> However, the mm of kworker is not valid. Therefore, check mm when killing
> accessing process.
> 
> Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>

Thanks for fixing.

Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>

Thanks,
Miaohe Lin


> ---
>  mm/memory-failure.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 14439806b5ef..7553917ce820 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -743,6 +743,9 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>  	};
>  	priv.tk.tsk = p;
>  
> +	if (!p->mm)
> +		return -EFAULT;
> +
>  	mmap_read_lock(p->mm);
>  	ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwp_walk_ops,
>  			      (void *)&priv);
> @@ -751,6 +754,7 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>  	else
>  		ret = 0;
>  	mmap_read_unlock(p->mm);
> +
>  	return ret > 0 ? -EHWPOISON : -EFAULT;
>  }
>  
> 

Re: [PATCH] mm,hwpoison: check mm when killing accessing process

[Naoya Horiguchi]

On Wed, Sep 14, 2022 at 02:49:35PM +0800, Shuai Xue wrote:
> The GHES code calls memory_failure_queue() from IRQ context to queue work
> into workqueue and schedule it on the current CPU. Then the work is
> processed in memory_failure_work_func() by kworker and calls
> memory_failure().
>
> When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
> SIGBUS with error virutal address") make memory_failure() call
> kill_accessing_process() that:
>
>     - holds mmap locking of current->mm
>     - does pagetable walk to find the error virtual address
>     - and sends SIGBUS to the current process with error info.
>
> However, the mm of kworker is not valid. Therefore, check mm when killing
> accessing process.
>
> Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>

Thank you for the patch, the fix itself makes sense to me.
I agree with this patch with applying comments from Andrew.

Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>

Re: [PATCH] mm,hwpoison: check mm when killing accessing process

[Shuai Xue]

在 2022/9/15 AM9:45, Miaohe Lin 写道:
> On 2022/9/14 14:49, Shuai Xue wrote:
>> The GHES code calls memory_failure_queue() from IRQ context to queue work
>> into workqueue and schedule it on the current CPU. Then the work is
>> processed in memory_failure_work_func() by kworker and calls
>> memory_failure().
>>
>> When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
>> SIGBUS with error virutal address") make memory_failure() call
>> kill_accessing_process() that:
>>
>>     - holds mmap locking of current->mm
>>     - does pagetable walk to find the error virtual address
>>     - and sends SIGBUS to the current process with error info.
>>
>> However, the mm of kworker is not valid. Therefore, check mm when killing
>> accessing process.
>>
>> Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
>> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> 
> Thanks for fixing.
> 
> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
> 
> Thanks,
> Miaohe Lin

Thank you for your review.

Cheers,
Shuai

> 
> 
>> ---
>>  mm/memory-failure.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 14439806b5ef..7553917ce820 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -743,6 +743,9 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>>  	};
>>  	priv.tk.tsk = p;
>>  
>> +	if (!p->mm)
>> +		return -EFAULT;
>> +
>>  	mmap_read_lock(p->mm);
>>  	ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwp_walk_ops,
>>  			      (void *)&priv);
>> @@ -751,6 +754,7 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
>>  	else
>>  		ret = 0;
>>  	mmap_read_unlock(p->mm);
>> +
>>  	return ret > 0 ? -EHWPOISON : -EFAULT;
>>  }
>>  
>>

Re: [PATCH] mm,hwpoison: check mm when killing accessing process

[Shuai Xue]

在 2022/9/15 AM9:48, Naoya Horiguchi 写道:
> On Wed, Sep 14, 2022 at 02:49:35PM +0800, Shuai Xue wrote:
>> The GHES code calls memory_failure_queue() from IRQ context to queue work
>> into workqueue and schedule it on the current CPU. Then the work is
>> processed in memory_failure_work_func() by kworker and calls
>> memory_failure().
>>
>> When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
>> SIGBUS with error virutal address") make memory_failure() call
>> kill_accessing_process() that:
>>
>>     - holds mmap locking of current->mm
>>     - does pagetable walk to find the error virtual address
>>     - and sends SIGBUS to the current process with error info.
>>
>> However, the mm of kworker is not valid. Therefore, check mm when killing
>> accessing process.
>>
>> Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
>> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> 
> Thank you for the patch, the fix itself makes sense to me.
> I agree with this patch with applying comments from Andrew.
> 
> Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>

Thank you for prompt review.

Cheers,
Shuai