Re: [PATCH] memcg_write_event_control(): fix a user-triggerable oops

[Michal Hocko <mhocko@suse.com>]

On Fri 26-07-24 06:43:57, Al Viro wrote:
> We are *not* guaranteed that anything past the terminating NUL
> is mapped (let alone initialized with anything sane).
>     

Fixes: 0dea116876ee ("cgroup: implement eventfd-based generic API for notifications")

> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> 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)

-- 
Michal Hocko
SUSE Labs