linux-kernel - Re: memory leak in sctp_process

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Date:   Thu, 30 May 2019 10:20:11 -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 Wed, May 29, 2019 at 08:37:57PM -0300, Marcelo Ricardo Leitner wrote:
> On Wed, May 29, 2019 at 03:07:09PM -0400, Neil Horman wrote:
> > --- a/net/sctp/sm_make_chunk.c
> > +++ b/net/sctp/sm_make_chunk.c
> > @@ -2419,9 +2419,12 @@ int sctp_process_init(struct sctp_association *asoc, struct sctp_chunk *chunk,
> >  	/* Copy cookie in case we need to resend COOKIE-ECHO. */
> >  	cookie = asoc->peer.cookie;
> >  	if (cookie) {
> > +		if (asoc->peer.cookie_allocated)
> > +			kfree(cookie);
> >  		asoc->peer.cookie = kmemdup(cookie, asoc->peer.cookie_len, gfp);
> >  		if (!asoc->peer.cookie)
> >  			goto clean_up;
> > +		asoc->peer.cookie_allocated=1;
> >  	}
> >  
> >  	/* RFC 2960 7.2.1 The initial value of ssthresh MAY be arbitrarily
> 
> What if we kmemdup directly at sctp_process_param(), as it's done for
> others already? Like SCTP_PARAM_RANDOM and SCTP_PARAM_HMAC_ALGO. I
> don't see a reason for SCTP_PARAM_STATE_COOKIE to be different
> here. This way it would be always allocated, and ready to be kfreed.
> 
> We still need to free it after the handshake, btw.
> 
>   Marcelo
> 

Still untested, but something like this?


diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index d2c7d0d2abc1..718b9917844e 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -393,6 +393,7 @@ void sctp_association_free(struct sctp_association *asoc)
 	kfree(asoc->peer.peer_random);
 	kfree(asoc->peer.peer_chunks);
 	kfree(asoc->peer.peer_hmacs);
+	kfree(asoc->peer.cookie);
 
 	/* Release the transport structures. */
 	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 72e74503f9fc..ff365f22a3c1 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -2431,14 +2431,6 @@ int sctp_process_init(struct sctp_association *asoc, struct sctp_chunk *chunk,
 	/* Peer Rwnd   : Current calculated value of the peer's rwnd.  */
 	asoc->peer.rwnd = asoc->peer.i.a_rwnd;
 
-	/* Copy cookie in case we need to resend COOKIE-ECHO. */
-	cookie = asoc->peer.cookie;
-	if (cookie) {
-		asoc->peer.cookie = kmemdup(cookie, asoc->peer.cookie_len, gfp);
-		if (!asoc->peer.cookie)
-			goto clean_up;
-	}
-
 	/* RFC 2960 7.2.1 The initial value of ssthresh MAY be arbitrarily
 	 * high (for example, implementations MAY use the size of the receiver
 	 * advertised window).
@@ -2607,7 +2599,9 @@ static int sctp_process_param(struct sctp_association *asoc,
 	case SCTP_PARAM_STATE_COOKIE:
 		asoc->peer.cookie_len =
 			ntohs(param.p->length) - sizeof(struct sctp_paramhdr);
-		asoc->peer.cookie = param.cookie->body;
+		asoc->peer.cookie = kmemdup(param.cookie->body, asoc->peer.cookie_len, gfp);
+		if (!asoc->peer.cookie)
+			retval = 0;
 		break;
 
 	case SCTP_PARAM_HEARTBEAT_INFO: