From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f78.google.com (mail-oa1-f78.google.com [209.85.160.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 557B13998BE for ; Tue, 8 Sep 2026 07:56:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.78 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788854196; cv=none; b=jp/DI4b7JDmJK+OQNhWzAp/H4iIY7Zu6K0jNbqVUnevBXKYAuItTgnKeq87Pwg/ZB6ewHdESA/7diibk2WBBka3JF8zTtlfIuhwF6qMJnrsy54jL7VmwApZ8EcOn4JyqYP4jwHDIiQTGC0LeI3q57PNh2RTDMnUdcBdJoDXfp6I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788854196; c=relaxed/simple; bh=v50rnfyNHekOw3pkFFRsKufh9AeiT5Wh2yTuQCZH/Cc=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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2002:a05:6820:2007:b0:6b5:ec2f:356e with SMTP id 006d021491bc7-6b5ec2f3676mr12495556eaf.31.1788854193238; Tue, 08 Sep 2026 00:56:33 -0700 (PDT) Date: Tue, 08 Sep 2026 00:56:33 -0700 In-Reply-To: <6a707c4f.13bfb6d0.1ecdd5.027e.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a9fbfb1.f614420e.2bf292.000a.GAE@google.com> Subject: Re: [syzbot] [trace?] WARNING in trace_rb_cpu_prepare From: syzbot To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, rostedt@goodmis.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 28924df2a08f Merge tag 'perf-tools-fixes-for-v7.3-2026-09-.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15761af9580000 kernel config: https://syzkaller.appspot.com/x/.config?x=b454dc6b1b7acd30 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 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15ea2af9580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10eb3af9580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/dec945b3d75e/disk-28924df2.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/4e41f1bc0876/vmlinux-28924df2.xz kernel image: https://storage.googleapis.com/syzbot-assets/ec9e83ddda2c/bzImage-28924df2.xz Bisection is inconclusive: the first bad commit could be any of: 6a80838814ee tracing: Add show_event_triggers to expose active event triggers 729757b96a66 tracing: Add show_event_filters to expose active event filters e4ef389e761b tracing: Check the return value of tracing_update_buffers() bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11d7d4f9580000 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 1 WARNING: kernel/trace/ring_buffer.c:8103 at trace_rb_cpu_prepare+0x330/0x3c0 kernel/trace/ring_buffer.c:8102, CPU#0: syz.2.31/6050 Modules linked in: CPU: 0 UID: 0 PID: 6050 Comm: syz.2.31 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 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:8102 Code: 08 f0 48 0f ab 03 31 c0 48 83 c4 30 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 87 2e fc ff 48 8d 3d 40 36 eb 0d 89 ee <67> 48 0f b9 3a b8 f4 ff ff ff eb d2 e8 6d 2e fc ff e9 ef fe ff ff RSP: 0018:ffffc90004a377d0 EFLAGS: 00010293 RAX: ffffffff81ca5f89 RBX: dffffc0000000000 RCX: ffff888027b3be80 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff8fb595d0 RBP: 0000000000000001 R08: ffffffff8fb1e77f R09: 1ffffffff1f63cef R10: dffffc0000000000 R11: fffffbfff1f63cf0 R12: 0000000000000000 R13: ffff88803e2a2908 R14: ffff88805d68b0a0 R15: 0000000000000000 FS: 00007f1a0c90e6c0(0000) GS:ffff888125bd1000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005555867aea68 CR3: 000000002b852000 CR4: 00000000003526f0 Call Trace: 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:383 [inline] alloc_buffer+0x188f/0x1d70 kernel/trace/ring_buffer.c:2917 __ring_buffer_alloc+0x2c/0x40 kernel/trace/ring_buffer.c:2959 allocate_trace_buffer+0x1d2/0x950 kernel/trace/trace.c:8465 allocate_trace_buffers kernel/trace/trace.c:8498 [inline] trace_array_create_systems+0x590/0xe60 kernel/trace/trace.c:8676 trace_array_create kernel/trace/trace.c:8719 [inline] instance_mkdir+0xd5/0x140 kernel/trace/trace.c:8734 tracefs_syscall_mkdir+0x11a/0x190 fs/tracefs/inode.c:121 vfs_mkdir+0x408/0x620 fs/namei.c:5410 filename_mkdirat+0x289/0x520 fs/namei.c:5443 __do_sys_mkdirat fs/namei.c:5464 [inline] __se_sys_mkdirat+0x35/0x150 fs/namei.c:5461 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f1a0d2ae159 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:00007f1a0c90e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000102 RAX: ffffffffffffffda RBX: 00007f1a0d535fa0 RCX: 00007f1a0d2ae159 RDX: 00000000000001ff RSI: 0000200000000140 RDI: ffffffffffffff9c RBP: 00007f1a0d345024 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f1a0d536038 R14: 00007f1a0d535fa0 R15: 00007ffc0a111b18 ---------------- 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: c3 ret 17: cc int3 18: cc int3 19: cc int3 1a: cc int3 1b: cc int3 1c: e8 87 2e fc ff call 0xfffc2ea8 21: 48 8d 3d 40 36 eb 0d lea 0xdeb3640(%rip),%rdi # 0xdeb3668 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 6d 2e fc ff call 0xfffc2ea8 3b: e9 ef fe ff ff jmp 0xffffff2f --- 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.