[PATCH v5 net] sctp: Free cookie before we memdup a new one

[Neil Horman <nhorman@tuxdriver.com>]

Based on comments from Xin, even after fixes for our recent syzbot
report of cookie memory leaks, its possible to get a resend of an INIT
chunk which would lead to us leaking cookie memory.

To ensure that we don't leak cookie memory, free any previously
allocated cookie first.

Change notes
v1->v2
update subsystem tag in subject (davem)
repeat kfree check for peer_random and peer_hmacs (xin)

v2->v3
net->sctp
also free peer_chunks

v3->v4
fix subject tags

v4->v5
remove cut line

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: syzbot+f7e9153b037eac9b1df8@syzkaller.appspotmail.com
CC: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
CC: Xin Long <lucien.xin@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: netdev@vger.kernel.org
---
 net/sctp/sm_make_chunk.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index f17908f5c4f3..9b0e5b0d701a 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -2583,6 +2583,8 @@ 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);
+		if (asoc->peer.cookie)
+			kfree(asoc->peer.cookie);
 		asoc->peer.cookie = kmemdup(param.cookie->body, asoc->peer.cookie_len, gfp);
 		if (!asoc->peer.cookie)
 			retval = 0;
@@ -2647,6 +2649,8 @@ static int sctp_process_param(struct sctp_association *asoc,
 			goto fall_through;
 
 		/* Save peer's random parameter */
+		if (asoc->peer.peer_random)
+			kfree(asoc->peer.peer_random);
 		asoc->peer.peer_random = kmemdup(param.p,
 					    ntohs(param.p->length), gfp);
 		if (!asoc->peer.peer_random) {
@@ -2660,6 +2664,8 @@ static int sctp_process_param(struct sctp_association *asoc,
 			goto fall_through;
 
 		/* Save peer's HMAC list */
+		if (asoc->peer.peer_hmacs)
+			kfree(asoc->peer.peer_hmacs);
 		asoc->peer.peer_hmacs = kmemdup(param.p,
 					    ntohs(param.p->length), gfp);
 		if (!asoc->peer.peer_hmacs) {
@@ -2675,6 +2681,8 @@ static int sctp_process_param(struct sctp_association *asoc,
 		if (!ep->auth_enable)
 			goto fall_through;
 
+		if (asoc->peer.peer_chunks)
+			kfree(asoc->peer.peer_chunks);
 		asoc->peer.peer_chunks = kmemdup(param.p,
 					    ntohs(param.p->length), gfp);
 		if (!asoc->peer.peer_chunks)
-- 
2.20.1