This is a note to let you know that I've just added the patch titled
mptcp: ensure snd_nxt is properly initialized on connect
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mptcp-ensure-snd_nxt-is-properly-initialized-on-connect.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From fb7a0d334894206ae35f023a82cad5a290fd7386 Mon Sep 17 00:00:00 2001
From: Paolo Abeni <pabeni@xxxxxxxxxx>
Date: Mon, 29 Apr 2024 20:00:31 +0200
Subject: mptcp: ensure snd_nxt is properly initialized on connect
From: Paolo Abeni <pabeni@xxxxxxxxxx>
commit fb7a0d334894206ae35f023a82cad5a290fd7386 upstream.
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: 8fd738049ac3 ("mptcp: fallback in case of simultaneous connect")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Christoph Paasch <cpaasch@xxxxxxxxx>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/485
Tested-by: Christoph Paasch <cpaasch@xxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240429-upstream-net-20240429-mptcp-snd_nxt-init-connect-v1-1-59ceac0a7dcb@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/mptcp/protocol.c | 3 +++
1 file changed, 3 insertions(+)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3754,6 +3754,9 @@ static int mptcp_connect(struct sock *sk
MPTCP_INC_STATS(sock_net(ssock->sk), MPTCP_MIB_TOKENFALLBACKINIT);
mptcp_subflow_early_fallback(msk, subflow);
}
+
+ WRITE_ONCE(msk->write_seq, subflow->idsn);
+ WRITE_ONCE(msk->snd_nxt, subflow->idsn);
if (likely(!__mptcp_check_fallback(msk)))
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVE);
Patches currently in stable-queue which might be from pabeni@xxxxxxxxxx are
queue-6.1/tipc-fix-a-possible-memleak-in-tipc_buf_append.patch
queue-6.1/nsh-restore-skb-protocol-data-mac_header-for-outer-h.patch
queue-6.1/net-l2tp-drop-flow-hash-on-forward.patch
queue-6.1/net-smc-fix-neighbour-and-rtable-leak-in-smc_ib_find.patch
queue-6.1/net-gro-add-flush-check-in-udp_gro_receive_segment.patch
queue-6.1/net-hns3-use-appropriate-barrier-function-after-sett.patch
queue-6.1/s390-qeth-fix-kernel-panic-after-setting-hsuid.patch
queue-6.1/net-hns3-using-user-configure-after-hardware-reset.patch
queue-6.1/net-hns3-change-type-of-numa_node_mask-as-nodemask_t.patch
queue-6.1/net-hns3-fix-port-vlan-filter-not-disabled-issue.patch
queue-6.1/net-bridge-fix-multicast-to-unicast-with-fraglist-gs.patch
queue-6.1/net-hns3-direct-return-when-receive-a-unknown-mailbo.patch
queue-6.1/mptcp-ensure-snd_nxt-is-properly-initialized-on-connect.patch
queue-6.1/net-hns3-release-ptp-resources-if-pf-initialization-.patch
queue-6.1/net-hns3-fix-kernel-crash-when-devlink-reload-during.patch
