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

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Message-ID: <ZqiSohxwLunBPnjT@tiehlicka>
Date: Tue, 30 Jul 2024 09:13:38 +0200
From: Michal Hocko <mhocko@...e.com>
To: viro@...nel.org
Cc: linux-fsdevel@...r.kernel.org, amir73il@...il.com, bpf@...r.kernel.org,
	brauner@...nel.org, cgroups@...r.kernel.org, kvm@...r.kernel.org,
	netdev@...r.kernel.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH 01/39] memcg_write_event_control(): fix a
 user-triggerable oops

On Tue 30-07-24 01:15:47, viro@...nel.org wrote:
> From: Al Viro <viro@...iv.linux.org.uk>
> 
> 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 <viro@...iv.linux.org.uk>

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

> ---
>  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