mptcp: consolidate suboption status

MPTCP maintains the received sub-options status is the bitmask carrying
the received suboptions and in several bitfields carrying per suboption
additional info.

Zeroing the bitmask before parsing is not enough to ensure a consistent
status, and the MPTCP code has to additionally clear some bitfiled
depending on the actually parsed suboption.

The above schema is fragile, and syzbot managed to trigger a path where
a relevant bitfield is not cleared/initialized:

  BUG: KMSAN: uninit-value in __mptcp_expand_seq net/mptcp/options.c:1030 [inline]
  BUG: KMSAN: uninit-value in mptcp_expand_seq net/mptcp/protocol.h:864 [inline]
  BUG: KMSAN: uninit-value in ack_update_msk net/mptcp/options.c:1060 [inline]
  BUG: KMSAN: uninit-value in mptcp_incoming_options+0x2036/0x3d30 net/mptcp/options.c:1209
   __mptcp_expand_seq net/mptcp/options.c:1030 [inline]
   mptcp_expand_seq net/mptcp/protocol.h:864 [inline]
   ack_update_msk net/mptcp/options.c:1060 [inline]
   mptcp_incoming_options+0x2036/0x3d30 net/mptcp/options.c:1209
   tcp_data_queue+0xb4/0x7be0 net/ipv4/tcp_input.c:5233
   tcp_rcv_established+0x1061/0x2510 net/ipv4/tcp_input.c:6264
   tcp_v4_do_rcv+0x7f3/0x11a0 net/ipv4/tcp_ipv4.c:1916
   tcp_v4_rcv+0x51df/0x5750 net/ipv4/tcp_ipv4.c:2351
   ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205
   ip_local_deliver_finish+0x336/0x500 net/ipv4/ip_input.c:233
   NF_HOOK include/linux/netfilter.h:314 [inline]
   ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254
   dst_input include/net/dst.h:460 [inline]
   ip_rcv_finish+0x4a2/0x520 net/ipv4/ip_input.c:447
   NF_HOOK include/linux/netfilter.h:314 [inline]
   ip_rcv+0xcd/0x380 net/ipv4/ip_input.c:567
   __netif_receive_skb_one_core net/core/dev.c:5704 [inline]
   __netif_receive_skb+0x319/0xa00 net/core/dev.c:5817
   process_backlog+0x4ad/0xa50 net/core/dev.c:6149
   __napi_poll+0xe7/0x980 net/core/dev.c:6902
   napi_poll net/core/dev.c:6971 [inline]
   net_rx_action+0xa5a/0x19b0 net/core/dev.c:7093
   handle_softirqs+0x1a0/0x7c0 kernel/softirq.c:561
   __do_softirq+0x14/0x1a kernel/softirq.c:595
   do_softirq+0x9a/0x100 kernel/softirq.c:462
   __local_bh_enable_ip+0x9f/0xb0 kernel/softirq.c:389
   local_bh_enable include/linux/bottom_half.h:33 [inline]
   rcu_read_unlock_bh include/linux/rcupdate.h:919 [inline]
   __dev_queue_xmit+0x2758/0x57d0 net/core/dev.c:4493
   dev_queue_xmit include/linux/netdevice.h:3168 [inline]
   neigh_hh_output include/net/neighbour.h:523 [inline]
   neigh_output include/net/neighbour.h:537 [inline]
   ip_finish_output2+0x187c/0x1b70 net/ipv4/ip_output.c:236
   __ip_finish_output+0x287/0x810
   ip_finish_output+0x4b/0x600 net/ipv4/ip_output.c:324
   NF_HOOK_COND include/linux/netfilter.h:303 [inline]
   ip_output+0x15f/0x3f0 net/ipv4/ip_output.c:434
   dst_output include/net/dst.h:450 [inline]
   ip_local_out net/ipv4/ip_output.c:130 [inline]
   __ip_queue_xmit+0x1f2a/0x20d0 net/ipv4/ip_output.c:536
   ip_queue_xmit+0x60/0x80 net/ipv4/ip_output.c:550
   __tcp_transmit_skb+0x3cea/0x4900 net/ipv4/tcp_output.c:1468
   tcp_transmit_skb net/ipv4/tcp_output.c:1486 [inline]
   tcp_write_xmit+0x3b90/0x9070 net/ipv4/tcp_output.c:2829
   __tcp_push_pending_frames+0xc4/0x380 net/ipv4/tcp_output.c:3012
   tcp_send_fin+0x9f6/0xf50 net/ipv4/tcp_output.c:3618
   __tcp_close+0x140c/0x1550 net/ipv4/tcp.c:3130
   __mptcp_close_ssk+0x74e/0x16f0 net/mptcp/protocol.c:2496
   mptcp_close_ssk+0x26b/0x2c0 net/mptcp/protocol.c:2550
   mptcp_pm_nl_rm_addr_or_subflow+0x635/0xd10 net/mptcp/pm_netlink.c:889
   mptcp_pm_nl_rm_subflow_received net/mptcp/pm_netlink.c:924 [inline]
   mptcp_pm_flush_addrs_and_subflows net/mptcp/pm_netlink.c:1688 [inline]
   mptcp_nl_flush_addrs_list net/mptcp/pm_netlink.c:1709 [inline]
   mptcp_pm_nl_flush_addrs_doit+0xe10/0x1630 net/mptcp/pm_netlink.c:1750
   genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
   genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
   genl_rcv_msg+0x1214/0x12c0 net/netlink/genetlink.c:1210
   netlink_rcv_skb+0x375/0x650 net/netlink/af_netlink.c:2542
   genl_rcv+0x40/0x60 net/netlink/genetlink.c:1219
   netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
   netlink_unicast+0xf52/0x1260 net/netlink/af_netlink.c:1347
   netlink_sendmsg+0x10da/0x11e0 net/netlink/af_netlink.c:1891
   sock_sendmsg_nosec net/socket.c:711 [inline]
   __sock_sendmsg+0x30f/0x380 net/socket.c:726
   ____sys_sendmsg+0x877/0xb60 net/socket.c:2583
   ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2637
   __sys_sendmsg net/socket.c:2669 [inline]
   __do_sys_sendmsg net/socket.c:2674 [inline]
   __se_sys_sendmsg net/socket.c:2672 [inline]
   __x64_sys_sendmsg+0x212/0x3c0 net/socket.c:2672
   x64_sys_call+0x2ed6/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:47
   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
   do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
   entry_SYSCALL_64_after_hwframe+0x77/0x7f

  Uninit was stored to memory at:
   mptcp_get_options+0x2c0f/0x2f20 net/mptcp/options.c:397
   mptcp_incoming_options+0x19a/0x3d30 net/mptcp/options.c:1150
   tcp_data_queue+0xb4/0x7be0 net/ipv4/tcp_input.c:5233
   tcp_rcv_established+0x1061/0x2510 net/ipv4/tcp_input.c:6264
   tcp_v4_do_rcv+0x7f3/0x11a0 net/ipv4/tcp_ipv4.c:1916
   tcp_v4_rcv+0x51df/0x5750 net/ipv4/tcp_ipv4.c:2351
   ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205
   ip_local_deliver_finish+0x336/0x500 net/ipv4/ip_input.c:233
   NF_HOOK include/linux/netfilter.h:314 [inline]
   ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254
   dst_input include/net/dst.h:460 [inline]
   ip_rcv_finish+0x4a2/0x520 net/ipv4/ip_input.c:447
   NF_HOOK include/linux/netfilter.h:314 [inline]
   ip_rcv+0xcd/0x380 net/ipv4/ip_input.c:567
   __netif_receive_skb_one_core net/core/dev.c:5704 [inline]
   __netif_receive_skb+0x319/0xa00 net/core/dev.c:5817
   process_backlog+0x4ad/0xa50 net/core/dev.c:6149
   __napi_poll+0xe7/0x980 net/core/dev.c:6902
   napi_poll net/core/dev.c:6971 [inline]
   net_rx_action+0xa5a/0x19b0 net/core/dev.c:7093
   handle_softirqs+0x1a0/0x7c0 kernel/softirq.c:561
   __do_softirq+0x14/0x1a kernel/softirq.c:595

  Uninit was stored to memory at:
   put_unaligned_be32 include/linux/unaligned.h:68 [inline]
   mptcp_write_options+0x17f9/0x3100 net/mptcp/options.c:1417
   mptcp_options_write net/ipv4/tcp_output.c:465 [inline]
   tcp_options_write+0x6d9/0xe90 net/ipv4/tcp_output.c:759
   __tcp_transmit_skb+0x294b/0x4900 net/ipv4/tcp_output.c:1414
   tcp_transmit_skb net/ipv4/tcp_output.c:1486 [inline]
   tcp_write_xmit+0x3b90/0x9070 net/ipv4/tcp_output.c:2829
   __tcp_push_pending_frames+0xc4/0x380 net/ipv4/tcp_output.c:3012
   tcp_send_fin+0x9f6/0xf50 net/ipv4/tcp_output.c:3618
   __tcp_close+0x140c/0x1550 net/ipv4/tcp.c:3130
   __mptcp_close_ssk+0x74e/0x16f0 net/mptcp/protocol.c:2496
   mptcp_close_ssk+0x26b/0x2c0 net/mptcp/protocol.c:2550
   mptcp_pm_nl_rm_addr_or_subflow+0x635/0xd10 net/mptcp/pm_netlink.c:889
   mptcp_pm_nl_rm_subflow_received net/mptcp/pm_netlink.c:924 [inline]
   mptcp_pm_flush_addrs_and_subflows net/mptcp/pm_netlink.c:1688 [inline]
   mptcp_nl_flush_addrs_list net/mptcp/pm_netlink.c:1709 [inline]
   mptcp_pm_nl_flush_addrs_doit+0xe10/0x1630 net/mptcp/pm_netlink.c:1750
   genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
   genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
   genl_rcv_msg+0x1214/0x12c0 net/netlink/genetlink.c:1210
   netlink_rcv_skb+0x375/0x650 net/netlink/af_netlink.c:2542
   genl_rcv+0x40/0x60 net/netlink/genetlink.c:1219
   netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
   netlink_unicast+0xf52/0x1260 net/netlink/af_netlink.c:1347
   netlink_sendmsg+0x10da/0x11e0 net/netlink/af_netlink.c:1891
   sock_sendmsg_nosec net/socket.c:711 [inline]
   __sock_sendmsg+0x30f/0x380 net/socket.c:726
   ____sys_sendmsg+0x877/0xb60 net/socket.c:2583
   ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2637
   __sys_sendmsg net/socket.c:2669 [inline]
   __do_sys_sendmsg net/socket.c:2674 [inline]
   __se_sys_sendmsg net/socket.c:2672 [inline]
   __x64_sys_sendmsg+0x212/0x3c0 net/socket.c:2672
   x64_sys_call+0x2ed6/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:47
   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
   do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
   entry_SYSCALL_64_after_hwframe+0x77/0x7f

  Uninit was stored to memory at:
   mptcp_pm_add_addr_signal+0x3d7/0x4c0
   mptcp_established_options_add_addr net/mptcp/options.c:666 [inline]
   mptcp_established_options+0x1b9b/0x3a00 net/mptcp/options.c:884
   tcp_established_options+0x2c4/0x7d0 net/ipv4/tcp_output.c:1012
   __tcp_transmit_skb+0x5b7/0x4900 net/ipv4/tcp_output.c:1333
   tcp_transmit_skb net/ipv4/tcp_output.c:1486 [inline]
   tcp_write_xmit+0x3b90/0x9070 net/ipv4/tcp_output.c:2829
   __tcp_push_pending_frames+0xc4/0x380 net/ipv4/tcp_output.c:3012
   tcp_send_fin+0x9f6/0xf50 net/ipv4/tcp_output.c:3618
   __tcp_close+0x140c/0x1550 net/ipv4/tcp.c:3130
   __mptcp_close_ssk+0x74e/0x16f0 net/mptcp/protocol.c:2496
   mptcp_close_ssk+0x26b/0x2c0 net/mptcp/protocol.c:2550
   mptcp_pm_nl_rm_addr_or_subflow+0x635/0xd10 net/mptcp/pm_netlink.c:889
   mptcp_pm_nl_rm_subflow_received net/mptcp/pm_netlink.c:924 [inline]
   mptcp_pm_flush_addrs_and_subflows net/mptcp/pm_netlink.c:1688 [inline]
   mptcp_nl_flush_addrs_list net/mptcp/pm_netlink.c:1709 [inline]
   mptcp_pm_nl_flush_addrs_doit+0xe10/0x1630 net/mptcp/pm_netlink.c:1750
   genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
   genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
   genl_rcv_msg+0x1214/0x12c0 net/netlink/genetlink.c:1210
   netlink_rcv_skb+0x375/0x650 net/netlink/af_netlink.c:2542
   genl_rcv+0x40/0x60 net/netlink/genetlink.c:1219
   netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
   netlink_unicast+0xf52/0x1260 net/netlink/af_netlink.c:1347
   netlink_sendmsg+0x10da/0x11e0 net/netlink/af_netlink.c:1891
   sock_sendmsg_nosec net/socket.c:711 [inline]
   __sock_sendmsg+0x30f/0x380 net/socket.c:726
   ____sys_sendmsg+0x877/0xb60 net/socket.c:2583
   ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2637
   __sys_sendmsg net/socket.c:2669 [inline]
   __do_sys_sendmsg net/socket.c:2674 [inline]
   __se_sys_sendmsg net/socket.c:2672 [inline]
   __x64_sys_sendmsg+0x212/0x3c0 net/socket.c:2672
   x64_sys_call+0x2ed6/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:47
   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
   do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
   entry_SYSCALL_64_after_hwframe+0x77/0x7f

  Uninit was stored to memory at:
   mptcp_pm_add_addr_received+0x95f/0xdd0 net/mptcp/pm.c:235
   mptcp_incoming_options+0x2983/0x3d30 net/mptcp/options.c:1169
   tcp_data_queue+0xb4/0x7be0 net/ipv4/tcp_input.c:5233
   tcp_rcv_state_process+0x2a38/0x49d0 net/ipv4/tcp_input.c:6972
   tcp_v4_do_rcv+0xbf9/0x11a0 net/ipv4/tcp_ipv4.c:1939
   tcp_v4_rcv+0x51df/0x5750 net/ipv4/tcp_ipv4.c:2351
   ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205
   ip_local_deliver_finish+0x336/0x500 net/ipv4/ip_input.c:233
   NF_HOOK include/linux/netfilter.h:314 [inline]
   ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254
   dst_input include/net/dst.h:460 [inline]
   ip_rcv_finish+0x4a2/0x520 net/ipv4/ip_input.c:447
   NF_HOOK include/linux/netfilter.h:314 [inline]
   ip_rcv+0xcd/0x380 net/ipv4/ip_input.c:567
   __netif_receive_skb_one_core net/core/dev.c:5704 [inline]
   __netif_receive_skb+0x319/0xa00 net/core/dev.c:5817
   process_backlog+0x4ad/0xa50 net/core/dev.c:6149
   __napi_poll+0xe7/0x980 net/core/dev.c:6902
   napi_poll net/core/dev.c:6971 [inline]
   net_rx_action+0xa5a/0x19b0 net/core/dev.c:7093
   handle_softirqs+0x1a0/0x7c0 kernel/softirq.c:561
   __do_softirq+0x14/0x1a kernel/softirq.c:595

  Local variable mp_opt created at:
   mptcp_incoming_options+0x119/0x3d30 net/mptcp/options.c:1127
   tcp_data_queue+0xb4/0x7be0 net/ipv4/tcp_input.c:5233

The current schema is too fragile; address the issue grouping all the
state-related data together and clearing the whole group instead of
just the bitmask. This also cleans-up the code a bit, as there is no
need to individually clear "random" bitfield in a couple of places
any more.

Fixes: 84dfe3677a6f ("mptcp: send out dedicated ADD_ADDR packet")
Cc: stable@vger.kernel.org
Reported-by: syzbot+23728c2df58b3bd175ad@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/6786ac51.050a0220.216c54.00a7.GAE@google.com
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/541
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250123-net-mptcp-syzbot-issues-v1-1-af73258a726f@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 21 insertions, 22 deletions

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 123f3f297284..fd2de185bc93 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -108,7 +108,6 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 			mp_opt->suboptions |= OPTION_MPTCP_DSS;
 			mp_opt->use_map = 1;
 			mp_opt->mpc_map = 1;
-			mp_opt->use_ack = 0;
 			mp_opt->data_len = get_unaligned_be16(ptr);
 			ptr += 2;
 		}
@@ -157,11 +156,6 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		pr_debug("DSS\n");
 		ptr++;
 
-		/* we must clear 'mpc_map' be able to detect MP_CAPABLE
-		 * map vs DSS map in mptcp_incoming_options(), and reconstruct
-		 * map info accordingly
-		 */
-		mp_opt->mpc_map = 0;
 		flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 		mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 		mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
@@ -369,8 +363,11 @@ void mptcp_get_options(const struct sk_buff *skb,
 	const unsigned char *ptr;
 	int length;
 
-	/* initialize option status */
-	mp_opt->suboptions = 0;
+	/* Ensure that casting the whole status to u32 is efficient and safe */
+	BUILD_BUG_ON(sizeof_field(struct mptcp_options_received, status) != sizeof(u32));
+	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct mptcp_options_received, status),
+				 sizeof(u32)));
+	*(u32 *)&mp_opt->status = 0;
 
 	length = (th->doff * 4) - sizeof(struct tcphdr);
 	ptr = (const unsigned char *)(th + 1);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 0174a5aad279..f6a207958459 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -149,22 +149,24 @@ struct mptcp_options_received {
 	u32	subflow_seq;
 	u16	data_len;
 	__sum16	csum;
-	u16	suboptions;
+	struct_group(status,
+		u16 suboptions;
+		u16 use_map:1,
+		    dsn64:1,
+		    data_fin:1,
+		    use_ack:1,
+		    ack64:1,
+		    mpc_map:1,
+		    reset_reason:4,
+		    reset_transient:1,
+		    echo:1,
+		    backup:1,
+		    deny_join_id0:1,
+		    __unused:2;
+	);
+	u8	join_id;
 	u32	token;
 	u32	nonce;
-	u16	use_map:1,
-		dsn64:1,
-		data_fin:1,
-		use_ack:1,
-		ack64:1,
-		mpc_map:1,
-		reset_reason:4,
-		reset_transient:1,
-		echo:1,
-		backup:1,
-		deny_join_id0:1,
-		__unused:2;
-	u8	join_id;
 	u64	thmac;
 	u8	hmac[MPTCPOPT_HMAC_LEN];
 	struct mptcp_addr_info addr;