KCSAN: data-race in sk_psock_drop / unix_stream

KCSAN: data-race in sk_psock_drop / unix_stream_sendmsg

Status: upstream: reported on 2026/02/25 12:24
Subsystems: net bpf
[Documentation on labels]
Reported-by: syzbot+87f770387a9e5dc6b79b@syzkaller.appspotmail.com
Fix commit: net: annotate data-races around sk->sk_{data_ready,write_space}
Patched on: [ci-upstream-linux-next-kasan-gce-root ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 8d16h, last: 8d16h

▶ ▼ ✨ AI Jobs (1)

ID	Workflow	Result	Correct	Bug	Created	Started	Finished	Revision	Error
ece1b702-1347-42e5-af92-7ce323429d26	assessment-kcsan	Benign: ✅ Confident: ✅	❓	KCSAN: data-race in sk_psock_drop / unix_stream_sendmsg	2026/02/23 15:12	2026/02/23 15:12	2026/02/23 15:16	305c0ec5cd886e2d13738e28e1b2df9b0ec20fc9

▶ ▼ Discussions (2)

Title	Replies (including bot)	Last reply
[PATCH net] net: annotate data-races around sk->sk_{data_ready,write_space}	3 (3)	2026/02/27 03:40
[syzbot] [net?] [bpf?] KCSAN: data-race in sk_psock_drop / unix_stream_sendmsg	0 (1)	2026/02/25 12:24

Sample crash report:

==================================================================
BUG: KCSAN: data-race in sk_psock_drop / unix_stream_sendmsg

write to 0xffff88810220dc08 of 8 bytes by task 3611 on cpu 1:
 sk_psock_stop_verdict net/core/skmsg.c:1311 [inline]
 sk_psock_drop+0x12f/0x270 net/core/skmsg.c:896
 sk_psock_put include/linux/skmsg.h:506 [inline]
 sock_map_unref+0x2a5/0x300 net/core/sock_map.c:185
 __sock_map_delete net/core/sock_map.c:426 [inline]
 sock_map_delete_from_link net/core/sock_map.c:439 [inline]
 sock_map_unlink net/core/sock_map.c:1608 [inline]
 sock_map_remove_links+0x228/0x340 net/core/sock_map.c:1623
 sock_map_close+0xa1/0x340 net/core/sock_map.c:1684
 unix_release+0x4e/0x80 net/unix/af_unix.c:1183
 __sock_release net/socket.c:662 [inline]
 sock_close+0x6b/0x150 net/socket.c:1455
 __fput+0x29b/0x650 fs/file_table.c:469
 fput_close_sync+0xad/0x190 fs/file_table.c:574
 __do_sys_close fs/open.c:1509 [inline]
 __se_sys_close fs/open.c:1494 [inline]
 __x64_sys_close+0x55/0xf0 fs/open.c:1494
 x64_sys_call+0x275d/0x3020 arch/x86/include/generated/asm/syscalls_64.h:4
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810220dc08 of 8 bytes by task 3605 on cpu 0:
 unix_stream_sendmsg+0x7f8/0xbb0 net/unix/af_unix.c:2480
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x5af/0x600 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
 x64_sys_call+0x194c/0x3020 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff8486dd00 -> 0xffffffff8472c9f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3605 Comm: syz.4.30 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================

Crashes (1):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Assets (help?)	Manager	Title
2026/02/19 03:14	upstream	23b0f90ba871	77d4d919	.config	console log	report			info	[disk image] [vmlinux] [kernel image]	ci2-upstream-kcsan-gce	KCSAN: data-race in sk_psock_drop / unix_stream_sendmsg

* ~~Struck through~~ repros no longer work on HEAD.