[syzbot] [trace?] WARNING in trace_rb_cpu_prepare

[syzbot <syzbot+fbe07bcf949966f3c00f@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    075b74841bd0 Linux 7.2-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16368cc6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cb17729fb04b1e3a
dashboard link: https://syzkaller.appspot.com/bug?extid=fbe07bcf949966f3c00f
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/678e77cc37b9/disk-075b7484.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cc9f771e7069/vmlinux-075b7484.xz
kernel image: https://storage.googleapis.com/syzbot-assets/71a5d4620b85/bzImage-075b7484.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fbe07bcf949966f3c00f@syzkaller.appspotmail.com

------------[ cut here ]------------
failed to allocate ring buffer on CPU 0
WARNING: kernel/trace/ring_buffer.c:7977 at trace_rb_cpu_prepare+0x330/0x3c0 kernel/trace/ring_buffer.c:7976, CPU#0: syz.5.14324/5698
Modules linked in:
CPU: 0 UID: 0 PID: 5698 Comm: syz.5.14324 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:trace_rb_cpu_prepare+0x332/0x3c0 kernel/trace/ring_buffer.c:7976
Code: 08 f0 48 0f ab 03 31 c0 48 83 c4 30 5b 41 5c 41 5d 41 5e 41 5f 5d e9 bd 2f 7e 09 cc e8 17 3b fc ff 48 8d 3d 70 05 ea 0d 89 ee <67> 48 0f b9 3a b8 f4 ff ff ff eb d2 e8 fd 3a fc ff e9 ef fe ff ff
RSP: 0018:ffffc90003ddf7e0 EFLAGS: 00010283
RAX: ffffffff81c9a0a9 RBX: dffffc0000000000 RCX: 0000000000080000
RDX: ffffc900125d3000 RSI: 0000000000000000 RDI: ffffffff8fb3a620
RBP: 0000000000000000 R08: ffffffff8fafa337 R09: 1ffffffff1f5f466
R10: dffffc0000000000 R11: fffffbfff1f5f467 R12: 0000000000000000
R13: ffff888025cfb380 R14: ffff88803896c0a0 R15: 0000000000000000
FS:  00007f467e1856c0(0000) GS:ffff888125c3e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f582bc58658 CR3: 0000000075292000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 cpuhp_invoke_callback+0x498/0x810 kernel/cpu.c:204
 cpuhp_issue_call+0x3f0/0x750 kernel/cpu.c:-1
 __cpuhp_state_add_instance_cpuslocked+0x225/0x560 kernel/cpu.c:2423
 __cpuhp_state_add_instance+0x25/0x40 kernel/cpu.c:2444
 cpuhp_state_add_instance include/linux/cpuhotplug.h:384 [inline]
 alloc_buffer+0x18aa/0x1d50 kernel/trace/ring_buffer.c:2830
 __ring_buffer_alloc+0x2c/0x40 kernel/trace/ring_buffer.c:2872
 allocate_trace_buffer+0x1d2/0x950 kernel/trace/trace.c:8412
 allocate_trace_buffers kernel/trace/trace.c:8445 [inline]
 trace_array_create_systems+0x590/0xe60 kernel/trace/trace.c:8623
 trace_array_create kernel/trace/trace.c:8666 [inline]
 instance_mkdir+0xd5/0x140 kernel/trace/trace.c:8681
 tracefs_syscall_mkdir+0x11a/0x190 fs/tracefs/inode.c:121
 vfs_mkdir+0x402/0x620 fs/namei.c:5276
 filename_mkdirat+0x289/0x520 fs/namei.c:5309
 __do_sys_mkdirat fs/namei.c:5330 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5327
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f467ff4e019
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f467e185028 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007f46801d6090 RCX: 00007f467ff4e019
RDX: 00000000000001ff RSI: 0000200000000200 RDI: ffffffffffffff9c
RBP: 00007f467ffe500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f46801d6128 R14: 00007f46801d6090 R15: 00007fffce30c118
 </TASK>
----------------
Code disassembly (best guess):
   0:	08 f0                	or     %dh,%al
   2:	48 0f ab 03          	bts    %rax,(%rbx)
   6:	31 c0                	xor    %eax,%eax
   8:	48 83 c4 30          	add    $0x30,%rsp
   c:	5b                   	pop    %rbx
   d:	41 5c                	pop    %r12
   f:	41 5d                	pop    %r13
  11:	41 5e                	pop    %r14
  13:	41 5f                	pop    %r15
  15:	5d                   	pop    %rbp
  16:	e9 bd 2f 7e 09       	jmp    0x97e2fd8
  1b:	cc                   	int3
  1c:	e8 17 3b fc ff       	call   0xfffc3b38
  21:	48 8d 3d 70 05 ea 0d 	lea    0xdea0570(%rip),%rdi        # 0xdea0598
  28:	89 ee                	mov    %ebp,%esi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	b8 f4 ff ff ff       	mov    $0xfffffff4,%eax
  34:	eb d2                	jmp    0x8
  36:	e8 fd 3a fc ff       	call   0xfffc3b38
  3b:	e9 ef fe ff ff       	jmp    0xffffff2f


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