syzbot


WARNING in rcu_check_gp_start_stall (4)

Status: upstream: reported on 2026/02/20 21:56
Reported-by: syzbot+e952109dd720d190f944@syzkaller.appspotmail.com
First crash: 99d, last: 8d05h
Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in rcu_check_gp_start_stall net prio:low -1 C done error 2928 1d03h 2654d 0/29 upstream: reported C repro on 2019/02/22 17:10
linux-5.15 WARNING in rcu_check_gp_start_stall (3) -1 6 205d 332d 0/3 auto-obsoleted due to no activity on 2026/02/15 02:49
linux-6.6 WARNING in rcu_check_gp_start_stall origin:lts-only -1 C done 132 1h16m 347d 0/2 upstream: reported C repro on 2025/06/17 13:49
linux-5.15 WARNING in rcu_check_gp_start_stall (2) -1 7 621d 766d 0/3 auto-obsoleted due to no activity on 2024/12/25 11:45
linux-5.15 WARNING in rcu_check_gp_start_stall -1 1 904d 904d 0/3 auto-obsoleted due to no activity on 2024/03/17 09:39
linux-6.1 WARNING in rcu_check_gp_start_stall origin:upstream missing-backport -1 C done 31 2d18h 986d 0/3 upstream: reported C repro on 2023/09/17 20:24

Sample crash report:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 948 at kernel/rcu/tree_stall.h:937 rcu_check_gp_start_stall+0x2dc/0x460 kernel/rcu/tree_stall.h:929
Modules linked in:
CPU: 1 PID: 948 Comm: syz.7.10017 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:rcu_check_gp_start_stall+0x2dc/0x460 kernel/rcu/tree_stall.h:937
Code: ff ff ff 48 c7 c7 20 1c 32 96 be 04 00 00 00 e8 3a f5 58 00 48 89 df b8 01 00 00 00 87 05 cc ba cc 14 85 c0 0f 85 19 ff ff ff <0f> 0b 48 81 ff 80 37 32 8c 74 47 48 c7 c0 c4 2b 8a 8d 48 c1 e8 03
RSP: 0018:ffffc90000dd0bb8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffffffff8c323780 RCX: ffffffff81656146
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffff8c323780
RBP: ffffc90000dd0e10 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff2c64384 R12: 0000000000002904
R13: ffff8880b913b258 R14: 0000000000000a02 R15: dffffc0000000000
FS:  00007fd921ce56c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd921ca2ff8 CR3: 000000004154b000 CR4: 00000000003506e0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000002
DR3: ffffffffefffff15 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 rcu_core+0x62b/0x1670 kernel/rcu/tree.c:2758
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:85 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x84/0x290 mm/kasan/generic.c:189
Code: 49 c1 e9 03 4b 8d 1c 21 49 89 df 4d 29 df 49 83 ff 10 7f 29 4d 85 ff 0f 84 38 01 00 00 4c 89 cb 48 f7 d3 4c 01 f3 41 80 3b 00 <0f> 85 86 01 00 00 49 ff c3 48 ff c3 75 ee e9 18 01 00 00 44 89 dd
RSP: 0018:ffffc9000324faf0 EFLAGS: 00000246
RAX: ffffffff812c5101 RBX: fffffffffffffffe RCX: ffffffff812c518e
RDX: 0000000000000001 RSI: 0000000000000030 RDI: ffffc9000324fc50
RBP: 0000000000000000 R08: ffffc9000324fc7f R09: 1ffff92000649f8f
R10: dffffc0000000000 R11: fffff52000649f8e R12: dffffc0000000001
R13: 00007ffffffff000 R14: 1ffff92000649f8a R15: 0000000000000006
 memset+0x1e/0x40 mm/kasan/shadow.c:44
 __fpu_restore_sig arch/x86/kernel/fpu/signal.c:315 [inline]
 fpu__restore_sig+0x23e/0x1060 arch/x86/kernel/fpu/signal.c:466
 restore_sigcontext arch/x86/kernel/signal.c:139 [inline]
 __ia32_sys_rt_sigreturn+0x5e4/0x760 arch/x86/kernel/signal.c:674
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd923a8be57
Code: 83 c8 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
RSP: 002b:00007fd921ce5028 EFLAGS: 00000246
RAX: 0000000000000049 RBX: 00007fd923d04fa0 RCX: 00007fd923a8be59
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000004
RBP: 00007fd923b21d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd923d05038 R14: 00007fd923d04fa0 R15: 00007fff53b84948
 </TASK>
----------------
Code disassembly (best guess):
   0:	49 c1 e9 03          	shr    $0x3,%r9
   4:	4b 8d 1c 21          	lea    (%r9,%r12,1),%rbx
   8:	49 89 df             	mov    %rbx,%r15
   b:	4d 29 df             	sub    %r11,%r15
   e:	49 83 ff 10          	cmp    $0x10,%r15
  12:	7f 29                	jg     0x3d
  14:	4d 85 ff             	test   %r15,%r15
  17:	0f 84 38 01 00 00    	je     0x155
  1d:	4c 89 cb             	mov    %r9,%rbx
  20:	48 f7 d3             	not    %rbx
  23:	4c 01 f3             	add    %r14,%rbx
  26:	41 80 3b 00          	cmpb   $0x0,(%r11)
* 2a:	0f 85 86 01 00 00    	jne    0x1b6 <-- trapping instruction
  30:	49 ff c3             	inc    %r11
  33:	48 ff c3             	inc    %rbx
  36:	75 ee                	jne    0x26
  38:	e9 18 01 00 00       	jmp    0x155
  3d:	44 89 dd             	mov    %r11d,%ebp

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/23 03:44 linux-5.15.y 93741761e5e3 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING in rcu_check_gp_start_stall
2026/03/06 15:49 linux-5.15.y 91d48252ad4b 41d8037d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING in rcu_check_gp_start_stall
2026/02/20 21:55 linux-5.15.y 3330a8d33e08 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING in rcu_check_gp_start_stall
* Struck through repros no longer work on HEAD.