sctp: fully initialize v4 addr in some functions

Syzbot found a crash:

  BUG: KMSAN: uninit-value in crc32_body lib/crc32.c:112 [inline]
  BUG: KMSAN: uninit-value in crc32_le_generic lib/crc32.c:179 [inline]
  BUG: KMSAN: uninit-value in __crc32c_le_base+0x4fa/0xd30 lib/crc32.c:202
  Call Trace:
    crc32_body lib/crc32.c:112 [inline]
    crc32_le_generic lib/crc32.c:179 [inline]
    __crc32c_le_base+0x4fa/0xd30 lib/crc32.c:202
    chksum_update+0xb2/0x110 crypto/crc32c_generic.c:90
    crypto_shash_update+0x4c5/0x530 crypto/shash.c:107
    crc32c+0x150/0x220 lib/libcrc32c.c:47
    sctp_csum_update+0x89/0xa0 include/net/sctp/checksum.h:36
    __skb_checksum+0x1297/0x12a0 net/core/skbuff.c:2640
    sctp_compute_cksum include/net/sctp/checksum.h:59 [inline]
    sctp_packet_pack net/sctp/output.c:528 [inline]
    sctp_packet_transmit+0x40fb/0x4250 net/sctp/output.c:597
    sctp_outq_flush_transports net/sctp/outqueue.c:1146 [inline]
    sctp_outq_flush+0x1823/0x5d80 net/sctp/outqueue.c:1194
    sctp_outq_uncork+0xd0/0xf0 net/sctp/outqueue.c:757
    sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1781 [inline]
    sctp_side_effects net/sctp/sm_sideeffect.c:1184 [inline]
    sctp_do_sm+0x8fe1/0x9720 net/sctp/sm_sideeffect.c:1155
    sctp_primitive_REQUESTHEARTBEAT+0x175/0x1a0 net/sctp/primitive.c:185
    sctp_apply_peer_addr_params+0x212/0x1d40 net/sctp/socket.c:2433
    sctp_setsockopt_peer_addr_params net/sctp/socket.c:2686 [inline]
    sctp_setsockopt+0x189bb/0x19090 net/sctp/socket.c:4672

The issue was caused by transport->ipaddr set with uninit addr param, which
was passed by:

  sctp_transport_init net/sctp/transport.c:47 [inline]
  sctp_transport_new+0x248/0xa00 net/sctp/transport.c:100
  sctp_assoc_add_peer+0x5ba/0x2030 net/sctp/associola.c:611
  sctp_process_param net/sctp/sm_make_chunk.c:2524 [inline]

where 'addr' is set by sctp_v4_from_addr_param(), and it doesn't initialize
the padding of addr->v4.

Later when calling sctp_make_heartbeat(), hbinfo.daddr(=transport->ipaddr)
will become the part of skb, and the issue occurs.

This patch is to fix it by initializing the padding of addr->v4 in
sctp_v4_from_addr_param(), as well as other functions that do the similar
thing, and these functions shouldn't trust that the caller initializes the
memory, as Marcelo suggested.

Reported-by: syzbot+6dcbfea81cd3d4dd0b02@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/protocol.c

@@ -227,6 +227,7 @@ static void sctp_v4_from_skb(union sctp_addr *addr, struct sk_buff *skb,
 		sa->sin_port = sh->dest;
 		sa->sin_addr.s_addr = ip_hdr(skb)->daddr;
 	}
+	memset(sa->sin_zero, 0, sizeof(sa->sin_zero));
 }
 
 /* Initialize an sctp_addr from a socket. */
@@ -235,6 +236,7 @@ static void sctp_v4_from_sk(union sctp_addr *addr, struct sock *sk)
 	addr->v4.sin_family = AF_INET;
 	addr->v4.sin_port = 0;
 	addr->v4.sin_addr.s_addr = inet_sk(sk)->inet_rcv_saddr;
+	memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
 }
 
 /* Initialize sk->sk_rcv_saddr from sctp_addr. */
@@ -257,6 +259,7 @@ static void sctp_v4_from_addr_param(union sctp_addr *addr,
 	addr->v4.sin_family = AF_INET;
 	addr->v4.sin_port = port;
 	addr->v4.sin_addr.s_addr = param->v4.addr.s_addr;
+	memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
 }
 
 /* Initialize an address parameter from a sctp_addr and return the length
@@ -281,6 +284,7 @@ static void sctp_v4_dst_saddr(union sctp_addr *saddr, struct flowi4 *fl4,
 	saddr->v4.sin_family = AF_INET;
 	saddr->v4.sin_port = port;
 	saddr->v4.sin_addr.s_addr = fl4->saddr;
+	memset(saddr->v4.sin_zero, 0, sizeof(saddr->v4.sin_zero));
 }
 
 /* Compare two addresses exactly. */
@@ -303,6 +307,7 @@ static void sctp_v4_inaddr_any(union sctp_addr *addr, __be16 port)
 	addr->v4.sin_family = AF_INET;
 	addr->v4.sin_addr.s_addr = htonl(INADDR_ANY);
 	addr->v4.sin_port = port;
+	memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
 }
 
 /* Is this a wildcard address? */