[PATCH 4.9 133/172] sctp: check af before verify address in sctp_addr_id2transport

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@xxxxxxxxx>


[ Upstream commit 912964eacb111551db73429719eb5fadcab0ff8a ]

Commit 6f29a1306131 ("sctp: sctp_addr_id2transport should verify the
addr before looking up assoc") invoked sctp_verify_addr to verify the
addr.

But it didn't check af variable beforehand, once users pass an address
with family = 0 through sockopt, sctp_get_af_specific will return NULL
and NULL pointer dereference will be caused by af->sockaddr_len.

This patch is to fix it by returning NULL if af variable is NULL.

Fixes: 6f29a1306131 ("sctp: sctp_addr_id2transport should verify the addr before looking up assoc")
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sctp/socket.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -239,7 +239,7 @@ static struct sctp_transport *sctp_addr_
 	union sctp_addr *laddr = (union sctp_addr *)addr;
 	struct sctp_transport *transport;
 
-	if (sctp_verify_addr(sk, laddr, af->sockaddr_len))
+	if (!af || sctp_verify_addr(sk, laddr, af->sockaddr_len))
 		return NULL;
 
 	addr_asoc = sctp_endpoint_lookup_assoc(sctp_sk(sk)->ep,