[moderation] [trace?] KCSAN: data-race in __rb_reserve_next / rb_iter_head_event

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d681d7ef617e Merge misc regression fixes that seem to have..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ec35f9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e3dbeec937af205c
dashboard link: https://syzkaller.appspot.com/bug?extid=530af6f1e5c230588975
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [linux-...@vger.kernel.org linux-tra...@vger.kernel.org mathieu....@efficios.com mhir...@kernel.org ros...@goodmis.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1c52a74f0ad1/disk-d681d7ef.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/23b0bba823e8/vmlinux-d681d7ef.xz
kernel image: https://storage.googleapis.com/syzbot-assets/22897f0a15a6/bzImage-d681d7ef.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+530af6...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __rb_reserve_next / rb_iter_head_event

write to 0xffff88810007e000 of 8 bytes by task 7217 on cpu 0:
__rb_reserve_next+0x5e9/0x6c0 kernel/trace/ring_buffer.c:4937
rb_reserve_next_event kernel/trace/ring_buffer.c:5011 [inline]
ring_buffer_lock_reserve+0x6b3/0x860 kernel/trace/ring_buffer.c:5070
__trace_buffer_lock_reserve kernel/trace/trace.h:1676 [inline]
trace_event_buffer_lock_reserve+0x14a/0x300 kernel/trace/trace.c:1924
trace_event_buffer_reserve+0x120/0x180 kernel/trace/trace_events.c:715
do_trace_event_raw_event_ipi_send_cpu include/trace/events/ipi.h:10 [inline]
trace_event_raw_event_ipi_send_cpu+0x82/0xf0 include/trace/events/ipi.h:10
__do_trace_ipi_send_cpu include/trace/events/ipi.h:10 [inline]
trace_ipi_send_cpu include/trace/events/ipi.h:10 [inline]
__resched_curr+0x1a8/0x1c0 kernel/sched/core.c:1225
resched_curr kernel/sched/core.c:1243 [inline]
wakeup_preempt kernel/sched/core.c:2302 [inline]
ttwu_do_activate+0x11f/0x230 kernel/sched/core.c:3841
ttwu_queue kernel/sched/core.c:4093 [inline]
try_to_wake_up+0x44f/0x6d0 kernel/sched/core.c:4431
autoremove_wake_function+0x10/0x50 kernel/sched/wait.c:404
__wake_up_common kernel/sched/wait.c:109 [inline]
__wake_up_common_lock kernel/sched/wait.c:126 [inline]
__wake_up_sync_key+0x52/0x80 kernel/sched/wait.c:193
__unix_dgram_recvmsg+0x3a4/0x860 net/unix/af_unix.c:2615
unix_dgram_recvmsg+0x7e/0x90 net/unix/af_unix.c:2689
sock_recvmsg_nosec+0xc2/0xf0 net/socket.c:1151
____sys_recvmsg+0x26f/0x280 net/socket.c:2931
___sys_recvmsg+0x11f/0x3a0 net/socket.c:2975
do_recvmmsg+0x1e5/0x560 net/socket.c:3070
__sys_recvmmsg net/socket.c:3144 [inline]
__do_sys_recvmmsg net/socket.c:3167 [inline]
__se_sys_recvmmsg net/socket.c:3160 [inline]
__x64_sys_recvmmsg+0xe5/0x170 net/socket.c:3160
x64_sys_call+0x77f/0x2550 arch/x86/include/generated/asm/syscalls_64.h:300
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810007e000 of 8 bytes by task 7202 on cpu 1:
rb_iter_head_event+0x178/0x280 kernel/trace/ring_buffer.c:3574
rb_iter_peek kernel/trace/ring_buffer.c:6252 [inline]
ring_buffer_iter_peek+0x486/0xb10 kernel/trace/ring_buffer.c:6393
peek_next_entry kernel/trace/trace.c:2349 [inline]
__find_next_entry+0x1a9/0x420 kernel/trace/trace.c:2398
trace_find_next_entry_inc kernel/trace/trace.c:2672 [inline]
s_next+0x10e/0x370 kernel/trace/trace.c:2711
traverse+0x1c1/0x3b0 fs/seq_file.c:121
seq_lseek+0xb5/0x170 fs/seq_file.c:324
tracing_lseek+0x63/0x80 kernel/trace/trace.c:3773
vfs_llseek fs/read_write.c:391 [inline]
ksys_lseek fs/read_write.c:404 [inline]
__do_sys_lseek fs/read_write.c:414 [inline]
__se_sys_lseek fs/read_write.c:412 [inline]
__x64_sys_lseek+0xe8/0x160 fs/read_write.c:412
x64_sys_call+0x156b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:9
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000249f0a0d5c -> 0x000000249f239ff0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7202 Comm: syz.0.1080 Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================


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