Re: [PATCH] mm/mempolicy: fix memory leak in weighted_interleave_auto_store()

[Joshua Hahn <joshua.hahnjy@gmail.com>]

On Tue, 31 Mar 2026 18:07:40 +0800 Jackie Liu <liu.yun@linux.dev> wrote:

> From: Jackie Liu <liuyun01@kylinos.cn>

Hi Jackie,

Thank you for the patch! Wow!! This is a great catch. As you note, the
trigger for this memory leak doesn't seem too difficult either.

Everything looks good, thank you! Have a great day : -)

Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>

> Add the missing kfree(new_wi_state) when the auto mode is already set
> to the requested value. When a user writes "false" to the auto sysfs
> interface and the current mode is already manual (mode_auto == false),
> the function returns early without freeing new_wi_state allocated at
> the beginning of the function. This can be triggered repeatedly from
> userspace, leaking memory on each write.
> 
> Fixes: e341f9c3c841 ("mm/mempolicy: Weighted Interleave Auto-tuning")
> Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
> ---
>  mm/mempolicy.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index cf92bd6a8226..9ac74178075b 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -3713,6 +3713,7 @@ static ssize_t weighted_interleave_auto_store(struct kobject *kobj,
>  			goto update_wi_state;
>  		if (input == old_wi_state->mode_auto) {
>  			mutex_unlock(&wi_state_lock);
> +			kfree(new_wi_state);
>  			return count;
>  		}
>  
> -- 
> 2.51.1