[syzbot] [net?] KCSAN: data-race in tcp_assign_congestion_control / tcp_v6_syn_recv_sock

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cee73b1e840c Merge tag 'riscv-for-linus-7.0-mw1' of git://..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1188e15a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a6d4a8c8877f1220
dashboard link: https://syzkaller.appspot.com/bug?extid=937b5bbb6a815b3e5d0b
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c607da3ff440/disk-cee73b1e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0ca19d705091/vmlinux-cee73b1e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6c9182a73e86/bzImage-cee73b1e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+937b5b...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in tcp_assign_congestion_control / tcp_v6_syn_recv_sock

read-write to 0xffff888103ccb073 of 1 bytes by interrupt on cpu 0:
tcp_assign_congestion_control+0x2d3/0x310 net/ipv4/tcp_cong.c:-1
tcp_ca_openreq_child+0x196/0x1d0 net/ipv4/tcp_minisocks.c:522
tcp_v4_syn_recv_sock+0x4ce/0xa90 net/ipv4/tcp_ipv4.c:1760
tcp_v6_syn_recv_sock+0xb1/0xe70 net/ipv6/tcp_ipv6.c:1340
tcp_check_req+0xddd/0x1150 net/ipv4/tcp_minisocks.c:927
tcp_v4_rcv+0xeda/0x1d90 net/ipv4/tcp_ipv4.c:2238
ip_protocol_deliver_rcu+0x395/0x790 net/ipv4/ip_input.c:207
ip_local_deliver_finish+0x1fc/0x2f0 net/ipv4/ip_input.c:241
NF_HOOK include/linux/netfilter.h:318 [inline]
ip_local_deliver+0xe8/0x1e0 net/ipv4/ip_input.c:262
dst_input include/net/dst.h:480 [inline]
ip_rcv_finish+0x194/0x1c0 net/ipv4/ip_input.c:453
NF_HOOK include/linux/netfilter.h:318 [inline]
ip_rcv+0x62/0x160 net/ipv4/ip_input.c:573
__netif_receive_skb_one_core net/core/dev.c:6149 [inline]
__netif_receive_skb net/core/dev.c:6262 [inline]
process_backlog+0x341/0x670 net/core/dev.c:6614
__napi_poll+0x5f/0x310 net/core/dev.c:7678
napi_poll net/core/dev.c:7741 [inline]
net_rx_action+0x452/0x930 net/core/dev.c:7893
handle_softirqs+0xb9/0x280 kernel/softirq.c:622
do_softirq+0x45/0x60 kernel/softirq.c:523
__local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450
local_bh_enable include/linux/bottom_half.h:33 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:924 [inline]
__dev_queue_xmit+0x139a/0x1f20 net/core/dev.c:4856
dev_queue_xmit include/linux/netdevice.h:3384 [inline]
neigh_hh_output include/net/neighbour.h:540 [inline]
neigh_output include/net/neighbour.h:554 [inline]
ip_finish_output2+0x705/0x8c0 net/ipv4/ip_output.c:237
__ip_finish_output net/ipv4/ip_output.c:-1 [inline]
ip_finish_output+0x114/0x2a0 net/ipv4/ip_output.c:325
NF_HOOK_COND include/linux/netfilter.h:307 [inline]
ip_output+0xbd/0x1c0 net/ipv4/ip_output.c:438
dst_output include/net/dst.h:470 [inline]
ip_local_out net/ipv4/ip_output.c:131 [inline]
__ip_queue_xmit+0xbb0/0xbf0 net/ipv4/ip_output.c:534
ip_queue_xmit+0x39/0x50 net/ipv4/ip_output.c:548
__tcp_transmit_skb+0x1af2/0x1f10 net/ipv4/tcp_output.c:1693
tcp_transmit_skb net/ipv4/tcp_output.c:1711 [inline]
tcp_write_xmit+0x1597/0x3640 net/ipv4/tcp_output.c:3064
__tcp_push_pending_frames+0x6d/0x1b0 net/ipv4/tcp_output.c:3247
tcp_push_pending_frames include/net/tcp.h:2282 [inline]
__tcp_sock_set_cork net/ipv4/tcp.c:3688 [inline]
tcp_sock_set_cork+0xe1/0x100 net/ipv4/tcp.c:3695
rds_tcp_xmit_path_complete+0x3b/0x50 net/rds/tcp_send.c:52
rds_send_xmit+0x128c/0x16f0 net/rds/send.c:480
rds_send_worker+0x44/0x1b0 net/rds/threads.c:200
process_one_work kernel/workqueue.c:3275 [inline]
process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3358
worker_thread+0x581/0x770 kernel/workqueue.c:3439
kthread+0x22a/0x280 kernel/kthread.c:467
ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888103ccb040 of 128 bytes by interrupt on cpu 1:
tcp_v6_syn_recv_sock+0x103/0xe70 net/ipv6/tcp_ipv6.c:1353
tcp_check_req+0xddd/0x1150 net/ipv4/tcp_minisocks.c:927
tcp_v4_rcv+0xeda/0x1d90 net/ipv4/tcp_ipv4.c:2238
ip_protocol_deliver_rcu+0x395/0x790 net/ipv4/ip_input.c:207
ip_local_deliver_finish+0x1fc/0x2f0 net/ipv4/ip_input.c:241
NF_HOOK include/linux/netfilter.h:318 [inline]
ip_local_deliver+0xe8/0x1e0 net/ipv4/ip_input.c:262
dst_input include/net/dst.h:480 [inline]
ip_rcv_finish+0x194/0x1c0 net/ipv4/ip_input.c:453
NF_HOOK include/linux/netfilter.h:318 [inline]
ip_rcv+0x62/0x160 net/ipv4/ip_input.c:573
__netif_receive_skb_one_core net/core/dev.c:6149 [inline]
__netif_receive_skb net/core/dev.c:6262 [inline]
process_backlog+0x341/0x670 net/core/dev.c:6614
__napi_poll+0x5f/0x310 net/core/dev.c:7678
napi_poll net/core/dev.c:7741 [inline]
net_rx_action+0x452/0x930 net/core/dev.c:7893
handle_softirqs+0xb9/0x280 kernel/softirq.c:622
do_softirq+0x45/0x60 kernel/softirq.c:523
__local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450
local_bh_enable include/linux/bottom_half.h:33 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:924 [inline]
__dev_queue_xmit+0x139a/0x1f20 net/core/dev.c:4856
dev_queue_xmit include/linux/netdevice.h:3384 [inline]
neigh_hh_output include/net/neighbour.h:540 [inline]
neigh_output include/net/neighbour.h:554 [inline]
ip_finish_output2+0x705/0x8c0 net/ipv4/ip_output.c:237
__ip_finish_output net/ipv4/ip_output.c:-1 [inline]
ip_finish_output+0x114/0x2a0 net/ipv4/ip_output.c:325
NF_HOOK_COND include/linux/netfilter.h:307 [inline]
ip_output+0xbd/0x1c0 net/ipv4/ip_output.c:438
dst_output include/net/dst.h:470 [inline]
ip_local_out net/ipv4/ip_output.c:131 [inline]
__ip_queue_xmit+0xbb0/0xbf0 net/ipv4/ip_output.c:534
ip_queue_xmit+0x39/0x50 net/ipv4/ip_output.c:548
__tcp_transmit_skb+0x1af2/0x1f10 net/ipv4/tcp_output.c:1693
tcp_transmit_skb net/ipv4/tcp_output.c:1711 [inline]
tcp_write_xmit+0x1597/0x3640 net/ipv4/tcp_output.c:3064
__tcp_push_pending_frames+0x6d/0x1b0 net/ipv4/tcp_output.c:3247
tcp_send_fin+0x58a/0x6a0 net/ipv4/tcp_output.c:3846
__tcp_close+0x67d/0x1130 net/ipv4/tcp.c:3258
tcp_close+0x28/0xd0 net/ipv4/tcp.c:3349
inet_release+0xcd/0xf0 net/ipv4/af_inet.c:437
inet6_release+0x3e/0x60 net/ipv6/af_inet6.c:487
__sock_release net/socket.c:662 [inline]
sock_release+0x4b/0xe0 net/socket.c:690
rds_tcp_accept_one+0x4a1/0x830 net/rds/tcp_listen.c:345
rds_tcp_accept_worker+0x1a/0x60 net/rds/tcp.c:524
process_one_work kernel/workqueue.c:3275 [inline]
process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3358
worker_thread+0x581/0x770 kernel/workqueue.c:3439
kthread+0x22a/0x280 kernel/kthread.c:467
ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 1918 Comm: kworker/u8:5 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Workqueue: krdsd rds_tcp_accept_worker
==================================================================


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