WARNING in check_buffer

Status: upstream: reported on 2026/09/20 14:21
Subsystems: trace
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+eb74dca0d1eb3ec227a7@syzkaller.appspotmail.com
First crash: 8d15h, last: 6h56m
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
2e922cda assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ WARNING in check_buffer 2026/09/18 00:34 2026/09/18 00:34 2026/09/18 01:09 8d7d05f1
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Title Replies (including bot) Last reply
[syzbot] [trace?] WARNING in check_buffer 1 (2) 2026/09/20 20:16
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 WARNING in check_buffer origin:lts-only -1 syz, C 6 2d08h 59d 0/3 upstream: reported C repro on 2026/07/27 18:46
linux-6.1 WARNING in check_buffer -1 14 2d08h 59d 0/3 upstream: reported on 2026/07/27 19:37

Sample crash report:
[CPU: 1]TIME DOES NOT MATCH expected:262542986296 actual:12294 delta:1 before:12293 after:12293 context:.
trace clock:trace_clock_counter+0x0/0x40
  [262542986295] PAGE TIME STAMP
 0x0:  [262542986295] delta:0 .
 0x18: [262542986295] delta:0 TIME EXTEND
 0x20:  [262542986295] delta:0 .
expected end:0x58 last event actually ended at:0x58
------------[ cut here ]------------
system_state != SYSTEM_BOOTING
WARNING: kernel/trace/ring_buffer.c:4783 at check_buffer.cold+0x1a2/0x1ef kernel/trace/ring_buffer.c:4783, CPU#1: syz.5.8933/29532
Modules linked in:
CPU: 1 UID: 0 PID: 29532 Comm: syz.5.8933 Tainted: G             L      syzkaller #0 PREEMPT(lazy) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:check_buffer.cold+0x1a2/0x1ef kernel/trace/ring_buffer.c:4783
Code: 03 0f b6 14 11 38 d0 7c 04 84 d2 75 5c 8b 2d ec 02 22 10 31 ff 89 ee e8 3f e4 e8 00 85 ed 0f 84 58 7f eb 00 e8 c2 e9 e8 00 90 <0f> 0b 90 e9 03 7d eb 00 49 c7 c7 00 5f f6 8b e9 51 fe ff ff e8 78
RSP: 0018:ffffc90002e77768 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 1ffff920005ceef3 RCX: 0000000000000002
RDX: ffff888051aa0000 RSI: ffffffff812327ae RDI: ffff888051aa0000
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000003006
R13: ffff88801d2dd800 R14: ffff88801f681000 R15: ffffffff8bf65aa0
FS:  000055555f1bf500(0000) GS:ffff888123c53000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555f1d29f8 CR3: 000000003c9d0000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 __rb_reserve_next.constprop.0+0x486/0x1640 kernel/trace/ring_buffer.c:4873
 rb_reserve_next_event kernel/trace/ring_buffer.c:5010 [inline]
 ring_buffer_lock_reserve+0x49a/0x1220 kernel/trace/ring_buffer.c:5069
 __trace_buffer_lock_reserve kernel/trace/trace.h:1677 [inline]
 trace_event_buffer_lock_reserve+0x123/0x6f0 kernel/trace/trace.c:1924
 trace_event_buffer_reserve+0x1f9/0x350 kernel/trace/trace_events.c:715
 do_trace_event_raw_event_sched_process_fork include/trace/events/sched.h:396 [inline]
 trace_event_raw_event_sched_process_fork+0x109/0x460 include/trace/events/sched.h:396
 __do_trace_sched_process_fork include/trace/events/sched.h:396 [inline]
 trace_sched_process_fork include/trace/events/sched.h:396 [inline]
 kernel_clone+0x461/0x9d0 kernel/fork.c:2779
 __do_sys_clone3+0x214/0x290 kernel/fork.c:3072
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f378c99ef49
Code: 90 b8 01 00 00 00 b9 01 00 00 00 eb ec 0f 1f 40 00 b8 ea ff ff ff 48 85 ff 74 28 48 85 d2 74 23 49 89 c8 b8 b3 01 00 00 0f 05 <48> 85 c0 7c 14 74 01 c3 31 ed 4c 89 c7 ff d2 48 89 c7 b8 3c 00 00
RSP: 002b:00007fff49a820f8 EFLAGS: 00000202 ORIG_RAX: 00000000000001b3
RAX: ffffffffffffffda RBX: 00007f378c95a4e0 RCX: 00007f378c99ef49
RDX: 00007f378c95a4e0 RSI: 0000000000000058 RDI: 00007fff49a82150
RBP: 00007f378d91e6c0 R08: 00007f378d91e6c0 R09: 00007fff49a82237
R10: 0000000000000008 R11: 0000000000000202 R12: ffffffffffffffe8
R13: 000000000000000b R14: 00007fff49a82150 R15: 00007fff49a82238
 </TASK>

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/24 23:07 upstream f49a343b305c 3c3cdf19 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in check_buffer
2026/09/23 20:36 upstream fe2ec83746e5 0a1606bc .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in check_buffer
2026/09/22 19:22 upstream c4e9f74da438 3e2106e5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in check_buffer
2026/09/22 19:22 upstream c4e9f74da438 3e2106e5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in check_buffer
2026/09/19 15:34 upstream 40288c9206c1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in check_buffer
2026/09/18 12:55 upstream 5dd1818b15d9 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in check_buffer
2026/09/17 19:33 upstream 4982d3552a3b 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root WARNING in check_buffer
2026/09/18 19:36 upstream 5dd1818b15d9 853b104b .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in check_buffer
2026/09/18 05:48 upstream 4982d3552a3b 8d7d05f1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in check_buffer
2026/09/22 19:15 upstream 50d05c7c76c9 3e2106e5 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in check_buffer
2026/09/20 16:33 upstream 50d05c7c76c9 853b104b .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in check_buffer
2026/09/16 14:09 upstream 50d05c7c76c9 b0e4c57e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in check_buffer
* Struck through repros no longer work on HEAD.