From: Mat Martineau mathew.j.martineau@linux.intel.com
[ Upstream commit 340fa6667a696338e707cd5531a9631093d1be29 ]
Recent changes exposed a bug where specifically-timed requests to the path manager netlink API could trigger a divide-by-zero in __tcp_select_window(), as syzkaller does:
divide error: 0000 [#1] SMP KASAN NOPTI CPU: 0 PID: 9667 Comm: syz-executor.0 Not tainted 5.14.0-rc6+ #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 RIP: 0010:__tcp_select_window+0x509/0xa60 net/ipv4/tcp_output.c:3016 Code: 44 89 ff e8 c9 29 e9 fd 45 39 e7 0f 8d 20 ff ff ff e8 db 28 e9 fd 44 89 e3 e9 13 ff ff ff e8 ce 28 e9 fd 44 89 e0 44 89 e3 99 <f7> 7c 24 04 29 d3 e9 fc fe ff ff e8 b7 28 e9 fd 44 89 f1 48 89 ea RSP: 0018:ffff888031ccf020 EFLAGS: 00010216 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000040000 RDX: 0000000000000000 RSI: ffff88811532c080 RDI: 0000000000000002 RBP: 0000000000000000 R08: ffffffff835807c2 R09: 0000000000000000 R10: 0000000000000004 R11: ffffed1020b92441 R12: 0000000000000000 R13: 1ffff11006399e08 R14: 0000000000000000 R15: 0000000000000000 FS: 00007fa4c8344700(0000) GS:ffff88811ae00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2f424000 CR3: 000000003e4e2003 CR4: 0000000000770ef0 PKRU: 55555554 Call Trace: tcp_select_window net/ipv4/tcp_output.c:264 [inline] __tcp_transmit_skb+0xc00/0x37a0 net/ipv4/tcp_output.c:1351 __tcp_send_ack.part.0+0x3ec/0x760 net/ipv4/tcp_output.c:3972 __tcp_send_ack net/ipv4/tcp_output.c:3978 [inline] tcp_send_ack+0x7d/0xa0 net/ipv4/tcp_output.c:3978 mptcp_pm_nl_addr_send_ack+0x1ab/0x380 net/mptcp/pm_netlink.c:654 mptcp_pm_remove_addr+0x161/0x200 net/mptcp/pm.c:58 mptcp_nl_remove_id_zero_address+0x197/0x460 net/mptcp/pm_netlink.c:1328 mptcp_nl_cmd_del_addr+0x98b/0xd40 net/mptcp/pm_netlink.c:1359 genl_family_rcv_msg_doit.isra.0+0x225/0x340 net/netlink/genetlink.c:731 genl_family_rcv_msg net/netlink/genetlink.c:775 [inline] genl_rcv_msg+0x341/0x5b0 net/netlink/genetlink.c:792 netlink_rcv_skb+0x148/0x430 net/netlink/af_netlink.c:2504 genl_rcv+0x24/0x40 net/netlink/genetlink.c:803 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x537/0x750 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x846/0xd80 net/netlink/af_netlink.c:1929 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg+0x14e/0x190 net/socket.c:724 ____sys_sendmsg+0x709/0x870 net/socket.c:2403 ___sys_sendmsg+0xff/0x170 net/socket.c:2457 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2486 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae
mptcp_pm_nl_addr_send_ack() was attempting to send a TCP ACK on the first subflow in the MPTCP socket's connection list without validating that the subflow was in a suitable connection state. To address this, always validate subflow state when sending extra ACKs on subflows for address advertisement or subflow priority change.
Fixes: 84dfe3677a6f ("mptcp: send out dedicated ADD_ADDR packet") Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/229 Co-developed-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Mat Martineau mathew.j.martineau@linux.intel.com Acked-by: Geliang Tang geliangtang@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/mptcp/pm_netlink.c | 10 ++-------- net/mptcp/protocol.c | 21 ++++++++++++--------- net/mptcp/protocol.h | 1 + 3 files changed, 15 insertions(+), 17 deletions(-)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 7b3794459783..89251cbe9f1a 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -540,7 +540,6 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk) subflow = list_first_entry_or_null(&msk->conn_list, typeof(*subflow), node); if (subflow) { struct sock *ssk = mptcp_subflow_tcp_sock(subflow); - bool slow;
spin_unlock_bh(&msk->pm.lock); pr_debug("send ack for %s%s%s", @@ -548,9 +547,7 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk) mptcp_pm_should_add_signal_ipv6(msk) ? " [ipv6]" : "", mptcp_pm_should_add_signal_port(msk) ? " [port]" : "");
- slow = lock_sock_fast(ssk); - tcp_send_ack(ssk); - unlock_sock_fast(ssk, slow); + mptcp_subflow_send_ack(ssk); spin_lock_bh(&msk->pm.lock); } } @@ -567,7 +564,6 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk, struct sock *ssk = mptcp_subflow_tcp_sock(subflow); struct sock *sk = (struct sock *)msk; struct mptcp_addr_info local; - bool slow;
local_address((struct sock_common *)ssk, &local); if (!addresses_equal(&local, addr, addr->port)) @@ -580,9 +576,7 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
spin_unlock_bh(&msk->pm.lock); pr_debug("send ack for mp_prio"); - slow = lock_sock_fast(ssk); - tcp_send_ack(ssk); - unlock_sock_fast(ssk, slow); + mptcp_subflow_send_ack(ssk); spin_lock_bh(&msk->pm.lock);
return 0; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index c018b591db0b..acbead7cf50f 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -427,19 +427,22 @@ static bool tcp_can_send_ack(const struct sock *ssk) (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_TIME_WAIT | TCPF_CLOSE | TCPF_LISTEN)); }
+void mptcp_subflow_send_ack(struct sock *ssk) +{ + bool slow; + + slow = lock_sock_fast(ssk); + if (tcp_can_send_ack(ssk)) + tcp_send_ack(ssk); + unlock_sock_fast(ssk, slow); +} + static void mptcp_send_ack(struct mptcp_sock *msk) { struct mptcp_subflow_context *subflow;
- mptcp_for_each_subflow(msk, subflow) { - struct sock *ssk = mptcp_subflow_tcp_sock(subflow); - bool slow; - - slow = lock_sock_fast(ssk); - if (tcp_can_send_ack(ssk)) - tcp_send_ack(ssk); - unlock_sock_fast(ssk, slow); - } + mptcp_for_each_subflow(msk, subflow) + mptcp_subflow_send_ack(mptcp_subflow_tcp_sock(subflow)); }
static void mptcp_subflow_cleanup_rbuf(struct sock *ssk) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 0f0c026c5f8b..6ac564d584c1 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -560,6 +560,7 @@ void __init mptcp_subflow_init(void); void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how); void mptcp_close_ssk(struct sock *sk, struct sock *ssk, struct mptcp_subflow_context *subflow); +void mptcp_subflow_send_ack(struct sock *ssk); void mptcp_subflow_reset(struct sock *ssk); void mptcp_sock_graft(struct sock *sk, struct socket *parent); struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk);