The patch titled Subject: mm,hwpoison: check mm when killing accessing process has been added to the -mm mm-hotfixes-unstable branch. Its filename is mmhwpoison-check-mm-when-killing-accessing-process.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Shuai Xue xueshuai@linux.alibaba.com Subject: mm,hwpoison: check mm when killing accessing process Date: Wed, 14 Sep 2022 14:49:35 +0800

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, resulting in a null-pointer dereference. So check mm when killing the accessing process.

Link: https://lkml.kernel.org/r/20220914064935.7851-1-xueshuai@linux.alibaba.com Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address") Signed-off-by: Shuai Xue xueshuai@linux.alibaba.com Cc: Huang Ying ying.huang@intel.com Cc: Baolin Wang baolin.wang@linux.alibaba.com Cc: Bixuan Cui cuibixuan@linux.alibaba.com Cc: Miaohe Lin linmiaohe@huawei.com Cc: Naoya Horiguchi naoya.horiguchi@nec.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/memory-failure.c | 4 ++++ 1 file changed, 4 insertions(+)

--- a/mm/memory-failure.c~mmhwpoison-check-mm-when-killing-accessing-process +++ a/mm/memory-failure.c @@ -745,6 +745,9 @@ static int kill_accessing_process(struct }; 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); @@ -753,6 +756,7 @@ static int kill_accessing_process(struct else ret = 0; mmap_read_unlock(p->mm); + return ret > 0 ? -EHWPOISON : -EFAULT; }

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Patches currently in -mm which might be from xueshuai@linux.alibaba.com are

mmhwpoison-check-mm-when-killing-accessing-process.patch