linux/net/mptcp
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_test.c mptcp: move crypto test to KUNIT 2020-06-26 16:21:39 -07:00
crypto.c kunit: mptcp: adhere to KUNIT formatting standard 2021-04-16 17:10:40 -07:00
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 mptcp: allow dumping subflow context to userspace 2020-03-29 22:14:48 -07:00
Kconfig kunit: mptcp: adhere to KUNIT formatting standard 2021-04-16 17:10:40 -07:00
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_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
pm.c mptcp: invoke MP_FAIL response when needed 2022-06-28 20:45:42 -07:00
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 mptcp: don't return sockets in foreign netns 2021-09-24 10:51:36 +01:00
token_test.c mptcp: don't return sockets in foreign netns 2021-09-24 10:51:36 +01:00
token.c mptcp: full disconnect implementation 2022-01-07 11:27:06 +00:00