+ mmhwpoison-check-mm-when-killing-accessing-process.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

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

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;
 }
 
_

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

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