CVE-2025-21707

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> mptcp: consolidate suboption status<br /> <br /> MPTCP maintains the received sub-options status is the bitmask carrying<br /> the received suboptions and in several bitfields carrying per suboption<br /> additional info.<br /> <br /> Zeroing the bitmask before parsing is not enough to ensure a consistent<br /> status, and the MPTCP code has to additionally clear some bitfiled<br /> depending on the actually parsed suboption.<br /> <br /> The above schema is fragile, and syzbot managed to trigger a path where<br /> a relevant bitfield is not cleared/initialized:<br /> <br /> BUG: KMSAN: uninit-value in __mptcp_expand_seq net/mptcp/options.c:1030 [inline]<br /> BUG: KMSAN: uninit-value in mptcp_expand_seq net/mptcp/protocol.h:864 [inline]<br /> BUG: KMSAN: uninit-value in ack_update_msk net/mptcp/options.c:1060 [inline]<br /> BUG: KMSAN: uninit-value in mptcp_incoming_options+0x2036/0x3d30 net/mptcp/options.c:1209<br /> __mptcp_expand_seq net/mptcp/options.c:1030 [inline]<br /> mptcp_expand_seq net/mptcp/protocol.h:864 [inline]<br /> ack_update_msk net/mptcp/options.c:1060 [inline]<br /> mptcp_incoming_options+0x2036/0x3d30 net/mptcp/options.c:1209<br /> tcp_data_queue+0xb4/0x7be0 net/ipv4/tcp_input.c:5233<br /> tcp_rcv_established+0x1061/0x2510 net/ipv4/tcp_input.c:6264<br /> tcp_v4_do_rcv+0x7f3/0x11a0 net/ipv4/tcp_ipv4.c:1916<br /> tcp_v4_rcv+0x51df/0x5750 net/ipv4/tcp_ipv4.c:2351<br /> ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205<br /> ip_local_deliver_finish+0x336/0x500 net/ipv4/ip_input.c:233<br /> NF_HOOK include/linux/netfilter.h:314 [inline]<br /> ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254<br /> dst_input include/net/dst.h:460 [inline]<br /> ip_rcv_finish+0x4a2/0x520 net/ipv4/ip_input.c:447<br /> NF_HOOK include/linux/netfilter.h:314 [inline]<br /> ip_rcv+0xcd/0x380 net/ipv4/ip_input.c:567<br /> __netif_receive_skb_one_core net/core/dev.c:5704 [inline]<br /> __netif_receive_skb+0x319/0xa00 net/core/dev.c:5817<br /> process_backlog+0x4ad/0xa50 net/core/dev.c:6149<br /> __napi_poll+0xe7/0x980 net/core/dev.c:6902<br /> napi_poll net/core/dev.c:6971 [inline]<br /> net_rx_action+0xa5a/0x19b0 net/core/dev.c:7093<br /> handle_softirqs+0x1a0/0x7c0 kernel/softirq.c:561<br /> __do_softirq+0x14/0x1a kernel/softirq.c:595<br /> do_softirq+0x9a/0x100 kernel/softirq.c:462<br /> __local_bh_enable_ip+0x9f/0xb0 kernel/softirq.c:389<br /> local_bh_enable include/linux/bottom_half.h:33 [inline]<br /> rcu_read_unlock_bh include/linux/rcupdate.h:919 [inline]<br /> __dev_queue_xmit+0x2758/0x57d0 net/core/dev.c:4493<br /> dev_queue_xmit include/linux/netdevice.h:3168 [inline]<br /> neigh_hh_output include/net/neighbour.h:523 [inline]<br /> neigh_output include/net/neighbour.h:537 [inline]<br /> ip_finish_output2+0x187c/0x1b70 net/ipv4/ip_output.c:236<br /> __ip_finish_output+0x287/0x810<br /> ip_finish_output+0x4b/0x600 net/ipv4/ip_output.c:324<br /> NF_HOOK_COND include/linux/netfilter.h:303 [inline]<br /> ip_output+0x15f/0x3f0 net/ipv4/ip_output.c:434<br /> dst_output include/net/dst.h:450 [inline]<br /> ip_local_out net/ipv4/ip_output.c:130 [inline]<br /> __ip_queue_xmit+0x1f2a/0x20d0 net/ipv4/ip_output.c:536<br /> ip_queue_xmit+0x60/0x80 net/ipv4/ip_output.c:550<br /> __tcp_transmit_skb+0x3cea/0x4900 net/ipv4/tcp_output.c:1468<br /> tcp_transmit_skb net/ipv4/tcp_output.c:1486 [inline]<br /> tcp_write_xmit+0x3b90/0x9070 net/ipv4/tcp_output.c:2829<br /> __tcp_push_pending_frames+0xc4/0x380 net/ipv4/tcp_output.c:3012<br /> tcp_send_fin+0x9f6/0xf50 net/ipv4/tcp_output.c:3618<br /> __tcp_close+0x140c/0x1550 net/ipv4/tcp.c:3130<br /> __mptcp_close_ssk+0x74e/0x16f0 net/mptcp/protocol.c:2496<br /> mptcp_close_ssk+0x26b/0x2c0 net/mptcp/protocol.c:2550<br /> mptcp_pm_nl_rm_addr_or_subflow+0x635/0xd10 net/mptcp/pm_netlink.c:889<br /> mptcp_pm_nl_rm_subflow_received net/mptcp/pm_netlink.c:924 [inline]<br /> mptcp_pm_flush_addrs_and_subflows net/mptcp/pm_netlink.c:1688 [inline]<br /> mptcp_nl_flush_addrs_list net/mptcp/pm_netlink.c:1709 [inline]<br /> mptcp_pm_nl_flush_addrs_doit+0xe10/0x1630 net/mptcp/pm_netlink.c:1750<br /> genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]<br /> <br /> ---truncated---