sctp: Free cookie before we memdup a new one

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
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 0 deletions

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 @@ do_addr_param:
         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 @@ do_addr_param:
                         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 @@ do_addr_param:
                         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 @@ do_addr_param:
                 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)