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linux-stable/net/mptcp
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Paolo Abeni fb7a0d3348 mptcp: ensure snd_nxt is properly initialized on connect 
Christoph reported a splat hinting at a corrupted snd_una:

  WARNING: CPU: 1 PID: 38 at net/mptcp/protocol.c:1005 __mptcp_clean_una+0x4b3/0x620 net/mptcp/protocol.c:1005
  Modules linked in:
  CPU: 1 PID: 38 Comm: kworker/1:1 Not tainted 6.9.0-rc1-gbbeac67456c9 #59
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
  Workqueue: events mptcp_worker
  RIP: 0010:__mptcp_clean_una+0x4b3/0x620 net/mptcp/protocol.c:1005
  Code: be 06 01 00 00 bf 06 01 00 00 e8 a8 12 e7 fe e9 00 fe ff ff e8
  	8e 1a e7 fe 0f b7 ab 3e 02 00 00 e9 d3 fd ff ff e8 7d 1a e7 fe
  	<0f> 0b 4c 8b bb e0 05 00 00 e9 74 fc ff ff e8 6a 1a e7 fe 0f 0b e9
  RSP: 0018:ffffc9000013fd48 EFLAGS: 00010293
  RAX: 0000000000000000 RBX: ffff8881029bd280 RCX: ffffffff82382fe4
  RDX: ffff8881003cbd00 RSI: ffffffff823833c3 RDI: 0000000000000001
  RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
  R10: 0000000000000000 R11: fefefefefefefeff R12: ffff888138ba8000
  R13: 0000000000000106 R14: ffff8881029bd908 R15: ffff888126560000
  FS:  0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f604a5dae38 CR3: 0000000101dac002 CR4: 0000000000170ef0
  Call Trace:
   <TASK>
   __mptcp_clean_una_wakeup net/mptcp/protocol.c:1055 [inline]
   mptcp_clean_una_wakeup net/mptcp/protocol.c:1062 [inline]
   __mptcp_retrans+0x7f/0x7e0 net/mptcp/protocol.c:2615
   mptcp_worker+0x434/0x740 net/mptcp/protocol.c:2767
   process_one_work+0x1e0/0x560 kernel/workqueue.c:3254
   process_scheduled_works kernel/workqueue.c:3335 [inline]
   worker_thread+0x3c7/0x640 kernel/workqueue.c:3416
   kthread+0x121/0x170 kernel/kthread.c:388
   ret_from_fork+0x44/0x50 arch/x86/kernel/process.c:147
   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
   </TASK>

When fallback to TCP happens early on a client socket, snd_nxt
is not yet initialized and any incoming ack will copy such value
into snd_una. If the mptcp worker (dumbly) tries mptcp-level
re-injection after such ack, that would unconditionally trigger a send
buffer cleanup using 'bad' snd_una values.

We could easily disable re-injection for fallback sockets, but such
dumb behavior already helped catching a few subtle issues and a very
low to zero impact in practice.

Instead address the issue always initializing snd_nxt (and write_seq,
for consistency) at connect time.

Fixes: 8fd738049a ("mptcp: fallback in case of simultaneous connect")
Cc: stable@vger.kernel.org
Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/485
Tested-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240429-upstream-net-20240429-mptcp-snd_nxt-init-connect-v1-1-59ceac0a7dcb@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 		2024-04-30 18:48:28 -07:00
..
Kconfig kunit: mptcp: adhere to KUNIT formatting standard 2021-04-16 17:10:40 -07:00
Makefile net: mptcp: use policy generated by YAML spec 2023-10-24 13:00:32 -07:00
bpf.c bpf: Add update_socket_protocol hook 2023-08-16 10:22:16 -07:00
crypto.c kunit: mptcp: adhere to KUNIT formatting standard 2021-04-16 17:10:40 -07:00
crypto_test.c mptcp: fill in missing MODULE_DESCRIPTION() 2023-12-17 20:54:22 +00:00
ctrl.c mptcp: add a new sysctl for make after break timeout 2023-10-25 12:23:33 -07:00
diag.c mptcp: drop duplicate header inclusions 2024-03-06 20:24:10 -08:00
fastopen.c mptcp: corner case locking for rx path fields initialization 2024-02-12 10:08:13 +00:00
mib.c mptcp: add CurrEstab MIB counter support 2024-01-02 13:32:45 +00:00
mib.h mptcp: add CurrEstab MIB counter support 2024-01-02 13:32:45 +00:00
mptcp_diag.c mptcp: drop duplicate header inclusions 2024-03-06 20:24:10 -08:00
mptcp_pm_gen.c mptcp: add token for get-addr in yaml 2024-03-04 13:07:45 +00:00
mptcp_pm_gen.h mptcp: add token for get-addr in yaml 2024-03-04 13:07:45 +00:00
options.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2024-02-29 14:24:56 -08:00
pm.c mptcp: update set_flags interfaces 2024-03-06 20:24:10 -08:00
pm_netlink.c mptcp: drop lookup_by_id in lookup_addr 2024-03-06 20:24:10 -08:00
pm_userspace.c mptcp: set error messages for set_flags 2024-03-06 20:24:10 -08:00
protocol.c mptcp: ensure snd_nxt is properly initialized on connect 2024-04-30 18:48:28 -07:00
protocol.h mptcp: annotate a data-race around sysctl_tcp_wmem[0] 2024-03-11 10:37:40 +00:00
sched.c mptcp: register default scheduler 2023-08-22 17:31:19 -07:00
sockopt.c mptcp: prevent BPF accessing lowat from a subflow socket. 2024-04-01 20:43:24 -07:00
subflow.c mptcp: don't account accept() of non-MPC client as fallback to TCP 2024-04-01 21:25:00 -07:00
syncookies.c mptcp: don't return sockets in foreign netns 2021-09-24 10:51:36 +01:00
token.c mptcp: add statistics for mptcp socket in use 2023-01-09 07:30:50 +00:00
token_test.c mptcp: token kunit: set protocol 2024-02-26 18:42:12 -08:00