[moderation] [trace?] KCSAN: data-race in probe_sched_switch / tracing_stop_cmdline_record

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f9a2394a2348 Merge tag 'mm-hotfixes-stable-2026-08-06-18-4..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=126f0fb9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=41eedfcd53c5fa394d5b
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/82bd4b0b2828/disk-f9a2394a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ab3cb0b1997d/vmlinux-f9a2394a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b0a8ddb2683a/bzImage-f9a2394a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+41eedf...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in probe_sched_switch / tracing_stop_cmdline_record

read-write to 0xffffffff893e0120 of 4 bytes by task 5456 on cpu 1:
tracing_stop_sched_switch kernel/trace/trace_sched_switch.c:120 [inline]
tracing_stop_cmdline_record+0x28/0xc0 kernel/trace/trace_sched_switch.c:140
__ftrace_event_enable_disable+0x323/0x4b0 kernel/trace/trace_events.c:821
ftrace_event_enable_disable kernel/trace/trace_events.c:907 [inline]
ftrace_clear_events kernel/trace/trace_events.c:1030 [inline]
ftrace_event_set_open+0xe6/0x200 kernel/trace/trace_events.c:2803
do_dentry_open+0x49f/0xa60 fs/open.c:947
vfs_open+0x37/0x1e0 fs/open.c:1052
do_open fs/namei.c:4700 [inline]
path_openat+0x1b39/0x2000 fs/namei.c:4863
do_file_open+0x16c/0x290 fs/namei.c:4892
do_sys_openat2+0xa0/0x130 fs/open.c:1368
do_sys_open fs/open.c:1374 [inline]
__do_sys_openat fs/open.c:1390 [inline]
__se_sys_openat fs/open.c:1385 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1385
x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff893e0120 of 4 bytes by task 5478 on cpu 0:
probe_sched_switch+0x46/0xa0 kernel/trace/trace_sched_switch.c:32
__do_trace_sched_switch include/trace/events/sched.h:220 [inline]
trace_sched_switch include/trace/events/sched.h:220 [inline]
__schedule+0xc23/0xd10 kernel/sched/core.c:7231
preempt_schedule_irq+0x2d/0x50 kernel/sched/core.c:7556
raw_irqentry_exit_cond_resched+0x4b/0x60 kernel/entry/common.c:145
irqentry_exit_to_kernel_mode_preempt+0x2b/0x40 include/linux/irq-entry-common.h:468
irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
irqentry_exit+0x7d/0x610 kernel/entry/common.c:167
asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:681
__preempt_count_dec_and_test arch/x86/include/asm/preempt.h:95 [inline]
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
_raw_spin_unlock_irqrestore+0x1a/0x30 kernel/locking/spinlock.c:198
__unix_dgram_recvmsg+0x3a4/0x860 net/unix/af_unix.c:2608
unix_dgram_recvmsg+0x7e/0x90 net/unix/af_unix.c:2682
sock_recvmsg_nosec+0xc2/0xf0 net/socket.c:1126
____sys_recvmsg+0x26f/0x280 net/socket.c:2902
___sys_recvmsg+0x11f/0x3a0 net/socket.c:2946
do_recvmmsg+0x1e5/0x560 net/socket.c:3041
__sys_recvmmsg net/socket.c:3115 [inline]
__do_sys_recvmmsg net/socket.c:3138 [inline]
__se_sys_recvmmsg net/socket.c:3131 [inline]
__x64_sys_recvmmsg+0xe5/0x170 net/socket.c:3131
x64_sys_call+0x80f/0x3020 arch/x86/include/generated/asm/syscalls_64.h:300
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000007e6 -> 0x000007e5

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5478 Comm: syz.9.8700 Tainted: G W syzkaller #0 PREEMPT(lazy)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================


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