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linux/net/mptcp
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Paolo Abeni 90918ef995 mptcp: more conservative check for zero probes 
[ Upstream commit 72377ab2d6 ]

Christoph reported that the MPTCP protocol can find the subflow-level
write queue unexpectedly not empty while crafting a zero-window probe,
hitting a warning:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 188 at net/mptcp/protocol.c:1312 mptcp_sendmsg_frag+0xc06/0xe70
Modules linked in:
CPU: 0 PID: 188 Comm: kworker/0:2 Not tainted 6.6.0-rc2-g1176aa719d7a #47
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
Workqueue: events mptcp_worker
RIP: 0010:mptcp_sendmsg_frag+0xc06/0xe70 net/mptcp/protocol.c:1312
RAX: 47d0530de347ff6a RBX: 47d0530de347ff6b RCX: ffff8881015d3c00
RDX: ffff8881015d3c00 RSI: 47d0530de347ff6b RDI: 47d0530de347ff6b
RBP: 47d0530de347ff6b R08: ffffffff8243c6a8 R09: ffffffff82042d9c
R10: 0000000000000002 R11: ffffffff82056850 R12: ffff88812a13d580
R13: 0000000000000001 R14: ffff88812b375e50 R15: ffff88812bbf3200
FS:  0000000000000000(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000695118 CR3: 0000000115dfc001 CR4: 0000000000170ef0
Call Trace:
 <TASK>
 __subflow_push_pending+0xa4/0x420 net/mptcp/protocol.c:1545
 __mptcp_push_pending+0x128/0x3b0 net/mptcp/protocol.c:1614
 mptcp_release_cb+0x218/0x5b0 net/mptcp/protocol.c:3391
 release_sock+0xf6/0x100 net/core/sock.c:3521
 mptcp_worker+0x6e8/0x8f0 net/mptcp/protocol.c:2746
 process_scheduled_works+0x341/0x690 kernel/workqueue.c:2630
 worker_thread+0x3a7/0x610 kernel/workqueue.c:2784
 kthread+0x143/0x180 kernel/kthread.c:388
 ret_from_fork+0x4d/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:304
 </TASK>

The root cause of the issue is that expectations are wrong: e.g. due
to MPTCP-level re-injection we can hit the critical condition.

Explicitly avoid the zero-window probe when the subflow write queue
is not empty and drop the related warnings.

Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/444
Fixes: f70cad1085 ("mptcp: stop relying on tcp_tx_skb_cache")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231018-send-net-20231018-v1-3-17ecb002e41d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-11-08 17:26:35 +01:00
..
crypto.c kunit: mptcp: adhere to KUNIT formatting standard 2021-04-16 17:10:40 -07:00
crypto_test.c mptcp: move crypto test to KUNIT 2020-06-26 16:21:39 -07:00
ctrl.c mptcp: faster active backup recovery 2021-08-14 11:37:25 +01:00
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 kunit: mptcp: adhere to KUNIT formatting standard 2021-04-16 17:10:40 -07:00
mib.c mptcp: add mibs counter for ignored incoming options 2022-03-02 11:47:53 +01:00
mib.h mptcp: add mibs counter for ignored incoming options 2022-03-02 11:47:53 +01:00
mptcp_diag.c mptcp: don't return sockets in foreign netns 2021-09-24 10:51:36 +01:00
options.c mptcp: use mptcp_schedule_work instead of open-coding it 2023-04-20 12:13:56 +02:00
pm.c mptcp: add mibs counter for ignored incoming options 2022-03-02 11:47:53 +01:00
pm_netlink.c mptcp: fix lockdep false positive in mptcp_pm_nl_create_listen_socket() 2023-03-22 13:31:35 +01:00
protocol.c mptcp: more conservative check for zero probes 2023-11-08 17:26:35 +01:00
protocol.h mptcp: Do TCP fallback on early DSS checksum failure 2022-05-25 14:42:07 +02:00
sockopt.c mptcp: remove tcp ulp setsockopt support 2021-12-22 09:32:43 +01:00
subflow.c mptcp: consolidate fallback and non fallback state machine 2023-07-05 18:25:04 +01:00
syncookies.c mptcp: don't return sockets in foreign netns 2021-09-24 10:51:36 +01:00
token.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