linux-kernel - Re: [syzbot] [trace?] WARNING in tracing_start

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Message-ID: <692f44a5.a70a0220.2ea503.00c8.GAE@google.com>
Date: Tue, 02 Dec 2025 11:57:26 -0800
From: syzbot <syzbot+ccdec3bfe0beec58a38d@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	mathieu.desnoyers@...icios.com, mhiramat@...nel.org, rostedt@...dmis.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [trace?] WARNING in tracing_start_tr

syzbot has found a reproducer for the following issue on:

HEAD commit:    4a26e7032d7d Merge tag 'core-bugs-2025-12-01' of git://git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12131512580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f17615e99b9a69ec
dashboard link: https://syzkaller.appspot.com/bug?extid=ccdec3bfe0beec58a38d
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12b492b4580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16b492b4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/240381b0df51/disk-4a26e703.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2bfd9dded97e/vmlinux-4a26e703.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e1ba9d12daee/bzImage-4a26e703.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ccdec3bfe0beec58a38d@...kaller.appspotmail.com

------------[ cut here ]------------
WARNING: kernel/trace/trace.c:2497 at tracing_start_tr+0x21d/0x2b0 kernel/trace/trace.c:2497, CPU#0: syz.3.186/6257
Modules linked in:
CPU: 0 UID: 0 PID: 6257 Comm: syz.3.186 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:tracing_start_tr+0x21d/0x2b0 kernel/trace/trace.c:2497
Code: 48 85 db 74 0d e8 73 1c fb ff 48 89 df e8 fb 42 fd ff e8 66 1c fb ff 4c 89 ef e8 be c5 ff ff e9 1e ff ff ff e8 54 1c fb ff 90 <0f> 0b 90 c7 83 94 00 00 00 00 00 00 00 e9 01 ff ff ff e8 3c 1c fb
RSP: 0018:ffffc90003777bd8 EFLAGS: 00010093
RAX: 0000000000000000 RBX: ffffffff8e250de0 RCX: ffffffff81c203e7
RDX: ffff888027699e80 RSI: ffffffff81c204dc RDI: 0000000000000005
RBP: 1ffff920006eef7c R08: 0000000000000005 R09: 0000000000000000
R10: 00000000ffffffff R11: 000000003ca71f67 R12: 00000000ffffffff
R13: dffffc0000000000 R14: 0000000000000293 R15: ffffffff8e250ec0
FS:  0000555561d28500(0000) GS:ffff888124ba8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000075090000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 buffer_subbuf_size_write+0x1ca/0x260 kernel/trace/trace.c:9702
 vfs_write+0x2a0/0x11d0 fs/read_write.c:684
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2c50f8f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe8ab04cc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2c511e5fa0 RCX: 00007f2c50f8f7c9
RDX: 0000000000000040 RSI: 0000200000000280 RDI: 0000000000000004
RBP: 00007f2c51013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c511e5fa0 R14: 00007f2c511e5fa0 R15: 0000000000000003
 </TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.