linux-kernel - Re: memory leak in sctp_process

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Message-ID: <20190531164319.GB3828@hmswarspite.think-freely.org>
Date:   Fri, 31 May 2019 12:43:19 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     syzbot <syzbot+f7e9153b037eac9b1df8@...kaller.appspotmail.com>,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, vyasevich@...il.com
Subject: Re: memory leak in sctp_process_init

On Fri, May 31, 2019 at 09:42:42AM -0300, Marcelo Ricardo Leitner wrote:
> On Thu, May 30, 2019 at 03:56:34PM -0400, Neil Horman wrote:
> > On Thu, May 30, 2019 at 12:17:05PM -0300, Marcelo Ricardo Leitner wrote:
> ...
> > > --- a/net/sctp/sm_sideeffect.c
> > > +++ b/net/sctp/sm_sideeffect.c
> > > @@ -898,6 +898,11 @@ static void sctp_cmd_new_state(struct sctp_cmd_seq *cmds,
> > >  						asoc->rto_initial;
> > >  	}
> > >  
> > > +	if (sctp_state(asoc, ESTABLISHED)) {
> > > +		kfree(asoc->peer.cookie);
> > > +		asoc->peer.cookie = NULL;
> > > +	}
> > > +
> > Not sure I follow why this is needed.  It doesn't hurt anything of course, but
> > if we're freeing in sctp_association_free, we don't need to duplicate the
> > operation here, do we?
> 
> This one would be to avoid storing the cookie throughout the entire
> association lifetime, as the cookie is only needed during the
> handshake.
> While the free in sctp_association_free will handle the freeing in
> case the association never enters established state.
> 

Ok, I see we do that with the peer_random and other allocated values as well
when they are no longer needed, but ew, I hate freeing in multiple places like
that.  I'll fix this up on monday, but I wonder if we can't consolidate that
somehow

Neil

> > >  	if (sctp_state(asoc, ESTABLISHED) ||
> > >  	    sctp_state(asoc, CLOSED) ||
> > >  	    sctp_state(asoc, SHUTDOWN_RECEIVED)) {
> > > 
> > > Also untested, just sharing the idea.
> > > 
> > >   Marcelo
> > > 
>