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linux/net/mptcp
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Li Xiasong 5dd8025a49 mptcp: fix soft lockup in mptcp_recvmsg() 
syzbot reported a soft lockup in mptcp_recvmsg() [0].

When receiving data with MSG_PEEK | MSG_WAITALL flags, the skb is not
removed from the sk_receive_queue. This causes sk_wait_data() to always
find available data and never perform actual waiting, leading to a soft
lockup.

Fix this by adding a 'last' parameter to track the last peeked skb.
This allows sk_wait_data() to make informed waiting decisions and prevent
infinite loops when MSG_PEEK is used.

[0]:
watchdog: BUG: soft lockup - CPU#2 stuck for 156s! [server:1963]
Modules linked in:
CPU: 2 UID: 0 PID: 1963 Comm: server Not tainted 6.19.0-rc8 #61 PREEMPT(none)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:sk_wait_data+0x15/0x190
Code: 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 56 41 55 41 54 49 89 f4 55 48 89 d5 53 48 89 fb <48> 83 ec 30 65 48 8b 05 17 a4 6b 01 48 89 44 24 28 31 c0 65 48 8b
RSP: 0018:ffffc90000603ca0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888102bf0800 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffc90000603d18 RDI: ffff888102bf0800
RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000101
R10: 0000000000000000 R11: 0000000000000075 R12: ffffc90000603d18
R13: ffff888102bf0800 R14: ffff888102bf0800 R15: 0000000000000000
FS:  00007f6e38b8c4c0(0000) GS:ffff8881b877e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055aa7bff1680 CR3: 0000000105cbe000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 mptcp_recvmsg+0x547/0x8c0 net/mptcp/protocol.c:2329
 inet_recvmsg+0x11f/0x130 net/ipv4/af_inet.c:891
 sock_recvmsg+0x94/0xc0 net/socket.c:1100
 __sys_recvfrom+0xb2/0x130 net/socket.c:2256
 __x64_sys_recvfrom+0x1f/0x30 net/socket.c:2267
 do_syscall_64+0x59/0x2d0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x76/0x7e arch/x86/entry/entry_64.S:131
RIP: 0033:0x7f6e386a4a1d
Code: 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8d 05 f1 de 2c 00 41 89 ca 8b 00 85 c0 75 20 45 31 c9 45 31 c0 b8 2d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 6b f3 c3 66 0f 1f 84 00 00 00 00 00 41 56 41
RSP: 002b:00007ffc3c4bb078 EFLAGS: 00000246 ORIG_RAX: 000000000000002d
RAX: ffffffffffffffda RBX: 000000000000861e RCX: 00007f6e386a4a1d
RDX: 00000000000003ff RSI: 00007ffc3c4bb150 RDI: 0000000000000004
RBP: 00007ffc3c4bb570 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000103 R11: 0000000000000246 R12: 00005605dbc00be0
R13: 00007ffc3c4bb650 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Fixes: 8e04ce45a8 ("mptcp: fix MSG_PEEK stream corruption")
Signed-off-by: Li Xiasong <lixiasong1@huawei.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260330120335.659027-1-lixiasong1@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 		2026-03-31 18:58:37 -07:00
..
Kconfig mptcp: select CRYPTO_LIB_UTILS instead of CRYPTO 2025-12-08 23:44:16 -08:00
Makefile mptcp: pm: split in-kernel PM specific code 2025-03-10 13:35:50 -07:00
bpf.c bpf: Add update_socket_protocol hook 2023-08-16 10:22:16 -07:00
crypto.c mptcp: use HMAC-SHA256 library instead of open-coded HMAC 2025-09-03 15:08:20 -07:00
crypto_test.c mptcp: fill in missing MODULE_DESCRIPTION() 2023-12-17 20:54:22 +00:00
ctrl.c mptcp: reset blackhole on success with non-loopback ifaces 2025-09-19 07:06:19 -07:00
diag.c tcp: ulp: diag: more info without CAP_NET_ADMIN 2025-03-07 19:39:53 -08:00
fastopen.c mptcp: borrow forward memory from subflow 2025-11-24 19:49:42 -08:00
mib.c mptcp: borrow forward memory from subflow 2025-11-24 19:49:42 -08:00
mib.h mptcp: borrow forward memory from subflow 2025-11-24 19:49:42 -08:00
mptcp_diag.c mptcp: introduce mptcp-level backlog 2025-11-24 19:49:43 -08:00
mptcp_pm_gen.c tools: ynl-gen: add regeneration comment 2025-11-25 19:20:42 -08:00
mptcp_pm_gen.h tools: ynl-gen: add regeneration comment 2025-11-25 19:20:42 -08:00
options.c mptcp: fallback earlier on simult connection 2025-12-23 09:12:25 +01:00
pm.c mptcp: pm: avoid sending RM_ADDR over same subflow 2026-03-04 18:21:12 -08:00
pm_kernel.c MPTCP: fix lock class name family in pm_nl_create_listen_socket 2026-03-19 09:37:48 -07:00
pm_netlink.c mptcp: pm: ignore unknown endpoint flags 2025-12-08 23:54:02 -08:00
pm_userspace.c mptcp: pm: rename 'subflows' to 'extra_subflows' 2025-09-26 17:44:04 -07:00
protocol.c mptcp: fix soft lockup in mptcp_recvmsg() 2026-03-31 18:58:37 -07:00
protocol.h mptcp: allow overridden write_space to be invoked 2026-02-10 19:54:21 -08:00
sched.c mptcp: sched: split validation part 2025-04-15 08:21:46 -07:00
sockopt.c mptcp: pm: in-kernel: record fullmesh endp nb 2025-11-04 17:15:06 -08:00
subflow.c Including fixes from IPsec, Bluetooth and netfilter 2026-02-26 08:00:13 -08:00
syncookies.c mptcp: don't return sockets in foreign netns 2021-09-24 10:51:36 +01:00
token.c mptcp: fix kdoc warnings 2026-02-06 20:35:06 -08:00
token_test.c mptcp: token kunit: set protocol 2024-02-26 18:42:12 -08:00