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

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Message-ID: <ZqNMfL6JmgHCJwBv@tiehlicka>
Date: Fri, 26 Jul 2024 09:13:00 +0200
From: Michal Hocko <mhocko@...e.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg_write_event_control(): fix a user-triggerable oops

On Fri 26-07-24 09:06:59, Michal Hocko wrote:
> 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@...iv.linux.org.uk>
> 
> Acked-by: Michal Hocko <mhocko@...e.com>

Btw. this should be
Cc: stable

> 
> > ---
> > 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

-- 
Michal Hocko
SUSE Labs