linux-kernel - Re: [PATCH v2 4/6] mm, hwpoison: fix possible use-after-free in mf_dax_kill

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Date:   Wed, 24 Aug 2022 00:36:22 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Miaohe Lin <linmiaohe@...wei.com>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/6] mm, hwpoison: fix possible use-after-free in
 mf_dax_kill_procs()

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@...wei.com>

Thank you for the update.

Acked-by: Naoya Horiguchi <naoya.horiguchi@....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