Paolo Abeni fa9e57468a mptcp: fix abba deadlock on fastopen ... Our CI reported lockdep splat in the fastopen code: ====================================================== WARNING: possible circular locking dependency detected 6.0.0.mptcp_f5e8bfe9878d+ #1558 Not tainted ------------------------------------------------------ packetdrill/1071 is trying to acquire lock: ffff8881bd198140 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_wait_for_connect+0x19c/0x310 but task is already holding lock: ffff8881b8346540 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_sendmsg+0xfdf/0x1740 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (k-sk_lock-AF_INET){+.+.}-{0:0}: __lock_acquire+0xb6d/0x1860 lock_acquire+0x1d8/0x620 lock_sock_nested+0x37/0xd0 inet_stream_connect+0x3f/0xa0 mptcp_connect+0x411/0x800 __inet_stream_connect+0x3ab/0x800 mptcp_stream_connect+0xac/0x110 __sys_connect+0x101/0x130 __x64_sys_connect+0x6e/0xb0 do_syscall_64+0x59/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #0 (sk_lock-AF_INET){+.+.}-{0:0}: check_prev_add+0x15e/0x2110 validate_chain+0xace/0xdf0 __lock_acquire+0xb6d/0x1860 lock_acquire+0x1d8/0x620 lock_sock_nested+0x37/0xd0 inet_wait_for_connect+0x19c/0x310 __inet_stream_connect+0x26c/0x800 tcp_sendmsg_fastopen+0x341/0x650 mptcp_sendmsg+0x109d/0x1740 sock_sendmsg+0xe1/0x120 __sys_sendto+0x1c7/0x2a0 __x64_sys_sendto+0xdc/0x1b0 do_syscall_64+0x59/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(k-sk_lock-AF_INET); lock(sk_lock-AF_INET); lock(k-sk_lock-AF_INET); lock(sk_lock-AF_INET); *** DEADLOCK *** 1 lock held by packetdrill/1071: #0: ffff8881b8346540 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_sendmsg+0xfdf/0x1740 ====================================================== The problem is caused by the blocking inet_wait_for_connect() releasing and re-acquiring the msk socket lock while the subflow socket lock is still held and the MPTCP socket requires that the msk socket lock must be acquired before the subflow socket lock. Address the issue always invoking tcp_sendmsg_fastopen() in an unblocking manner, and later eventually complete the blocking __inet_stream_connect() as needed. Fixes: d98a82a6af ("mptcp: handle defer connect in mptcp_sendmsg") Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com> Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>		2022-10-24 21:13:56 -07:00
..
bpf.c	bpf: Add bpf_skc_to_mptcp_sock_proto	2022-05-20 15:29:00 -07:00
crypto.c
crypto_test.c
ctrl.c	mptcp: Add a per-namespace sysctl to set the default path manager type	2022-04-29 17:25:14 -07:00
diag.c
Kconfig
Makefile	Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next	2022-05-23 16:07:14 -07:00
mib.c	mptcp: add more offered MIBs counter	2022-05-05 19:00:16 -07:00
mib.h	mptcp: add more offered MIBs counter	2022-05-05 19:00:16 -07:00
mptcp_diag.c	tcp: Access &tcp_hashinfo via net.	2022-09-20 10:21:49 -07:00
options.c	tcp: Fix data-races around sysctl_tcp_workaround_signed_windows.	2022-07-22 12:06:17 +01:00
pm.c	mptcp: invoke MP_FAIL response when needed	2022-06-28 20:45:42 -07:00
pm_netlink.c	mptcp: account memory allocation in mptcp_nl_cmd_add_addr() to user	2022-09-15 12:01:02 +02:00
pm_userspace.c	mptcp: update MIB_RMSUBFLOW in cmd_sf_destroy	2022-07-06 12:50:26 +01:00
protocol.c	mptcp: fix abba deadlock on fastopen	2022-10-24 21:13:56 -07:00
protocol.h	mptcp: factor out mptcp_connect()	2022-10-24 21:13:55 -07:00
sockopt.c	mptcp: add TCP_FASTOPEN_CONNECT socket option	2022-09-28 18:52:03 -07:00
subflow.c	mptcp: set msk local address earlier	2022-10-24 21:13:55 -07:00
syncookies.c
token.c
token_test.c