Subject: Re: [PATCH 01/39] memcg_write_event_control(): fix a user-triggerable oops

From: Michal Hocko <[email-masked]>
Date: Tue, 30 Jul 2024 09:13:38 +0200

On Tue 30-07-24 01:15:47, [email-masked] wrote:
> From: Al Viro <[email-masked]>
> 
> we are *not* guaranteed that anything past the terminating NUL
> is mapped (let alone initialized with anything sane).
> 
> [the sucker got moved in mainline]
> 

You could have preserved
Fixes: 0dea116876ee ("cgroup: implement eventfd-based generic API for notifications")
Cc: stable

> Signed-off-by: Al Viro <[email-masked]>

and
Acked-by: Michal Hocko <[email-masked]>

> ---
>  mm/memcontrol-v1.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
> index 2aeea4d8bf8e..417c96f2da28 100644
> --- a/mm/memcontrol-v1.c
> +++ b/mm/memcontrol-v1.c
> @@ -1842,9 +1842,12 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
>  	buf = endp + 1;
>  
>  	cfd = simple_strtoul(buf, &endp, 10);
> -	if ((*endp != ' ') && (*endp != '\0'))
> +	if (*endp == '\0')
> +		buf = endp;
> +	else if (*endp == ' ')
> +		buf = endp + 1;
> +	else
>  		return -EINVAL;
> -	buf = endp + 1;
>  
>  	event = kzalloc(sizeof(*event), GFP_KERNEL);
>  	if (!event)
> -- 
> 2.39.2
> 

-- 
Michal Hocko
SUSE Labs