After kill_procs(), tk will be freed without being removed from the to_kill
list. In the next iteration, the freed list entry in the to_kill list will
be accessed, thus leading to use-after-free issue. Adding list_del() in
kill_procs() to fix the issue.

Fixes: c36e20249571 ("mm: introduce mf_dax_kill_procs() for fsdax case")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/memory-failure.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 1d79e693f1b9..f8262f577baf 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -413,7 +413,7 @@ static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
 {
 	struct to_kill *tk, *next;
 
-	list_for_each_entry_safe (tk, next, to_kill, nd) {
+	list_for_each_entry_safe(tk, next, to_kill, nd) {
 		if (forcekill) {
 			/*
 			 * In case something went wrong with munmapping
@@ -437,6 +437,7 @@ static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
 				pr_err("%#lx: Cannot send advisory machine check signal to %s:%d\n",
 				       pfn, tk->tsk->comm, tk->tsk->pid);
 		}
+		list_del(&tk->nd);
 		put_task_struct(tk->tsk);
 		kfree(tk);
 	}
-- 
2.23.0

On Tue, Aug 23, 2022 at 11:23:44AM +0800, Miaohe Lin wrote:
> After kill_procs(), tk will be freed without being removed from the to_kill
> list. In the next iteration, the freed list entry in the to_kill list will
> be accessed, thus leading to use-after-free issue. Adding list_del() in
> kill_procs() to fix the issue.
> 
> Fixes: c36e20249571 ("mm: introduce mf_dax_kill_procs() for fsdax case")
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>

Thank you for the update.

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

> ---
>  mm/memory-failure.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 1d79e693f1b9..f8262f577baf 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -413,7 +413,7 @@ static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
>  {
>  	struct to_kill *tk, *next;
>  
> -	list_for_each_entry_safe (tk, next, to_kill, nd) {
> +	list_for_each_entry_safe(tk, next, to_kill, nd) {
>  		if (forcekill) {
>  			/*
>  			 * In case something went wrong with munmapping
> @@ -437,6 +437,7 @@ static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
>  				pr_err("%#lx: Cannot send advisory machine check signal to %s:%d\n",
>  				       pfn, tk->tsk->comm, tk->tsk->pid);
>  		}
> +		list_del(&tk->nd);
>  		put_task_struct(tk->tsk);
>  		kfree(tk);
>  	}
> -- 
> 2.23.0