mm,hwpoison: check mm when killing accessing process

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 cb847afd775e ("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.

[akpm@linux-foundation.org: remove unrelated whitespace alteration]
Link: https://lkml.kernel.org/r/20220914064935.7851-1-xueshuai@linux.alibaba.com
Fixes: cb847afd775e ("mm,hwpoison: send SIGBUS with error virutal address")
Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Bixuan Cui <cuibixuan@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index e424a9dac749b18df25f88533eb5b9ceb1b3d6d2..e7ac570dda75dd1d63a7380a095de4a2d25a0f5c 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -745,6 +745,9 @@ 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);