=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/sched/sch_api.c:304 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
4 locks held by syz-executor/4184:
 #0: ffffffff8c8af838 (tomoyo_ss){....}-{0:0}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
 #1: ffffc90000dd0c00 ((&q->perturb_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
 #1: ffffc90000dd0c00 ((&q->perturb_timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1441
 #2: ffff888025da6908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #2: ffff888025da6908 (&sch->q.lock){+.-.}-{2:2}, at: sfq_perturbation+0x14d/0x20d0 net/sched/sch_sfq.c:610
 #3: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 1 PID: 4184 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 qdisc_lookup+0xa6/0x650 net/sched/sch_api.c:304
 qdisc_tree_reduce_backlog+0x190/0x430 net/sched/sch_api.c:783
 sfq_rehash net/sched/sch_sfq.c:598 [inline]
 sfq_perturbation+0x1f5e/0x20d0 net/sched/sch_sfq.c:613
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1451
 expire_timers kernel/time/timer.c:1496 [inline]
 __run_timers+0x53a/0x7f0 kernel/time/timer.c:1767
 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:check_kcov_mode kernel/kcov.c:183 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x32/0x60 kernel/kcov.c:206
Code: 14 50 89 7e 65 8b 15 15 50 89 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 34 16 00 00 00 74 2c 8b 91 10 16 00 00 <83> fa 02 75 21 48 8b 91 18 16 00 00 48 8b 32 48 8d 7e 01 8b 89 14
RSP: 0018:ffffc90002ecf5c8 EFLAGS: 00000246
RAX: ffffffff83a3947d RBX: dffffc0000000000 RCX: ffff88801b9f5940
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: ffff88807d9c0301 R08: ffff88807d9c033f R09: 1ffff1100fb38067
R10: dffffc0000000000 R11: ffffed100fb38068 R12: 0000000000000054
R13: 0000000000000e10 R14: 0000000000000053 R15: ffff88807d9c0330
 tomoyo_check_acl+0x30d/0x3f0 security/tomoyo/domain.c:183
 tomoyo_path_permission+0x1b4/0x380 security/tomoyo/file.c:586
 tomoyo_check_open_permission+0x275/0x410 security/tomoyo/file.c:777
 security_file_open+0x5e/0xa0 security/security.c:1668
 do_dentry_open+0x322/0xf80 fs/open.c:813
 do_open fs/namei.c:3616 [inline]
 path_openat+0x26f5/0x2fa0 fs/namei.c:3750
 do_filp_open+0x1e2/0x410 fs/namei.c:3777
 do_sys_openat2+0x150/0x4b0 fs/open.c:1255
 do_sys_open fs/open.c:1271 [inline]
 __do_sys_openat fs/open.c:1287 [inline]
 __se_sys_openat fs/open.c:1282 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1282
 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: 0033:0x7f812e6ac78e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffdbaefa778 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000055556e276500 RCX: 00007f812e6ac78e
RDX: 0000000000000002 RSI: 00007ffdbaefa8c0 RDI: ffffffffffffff9c
RBP: 00007ffdbaefa86c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000003e
R13: 00000000000927c0 R14: 000000000001c3df R15: 00007ffdbaefa8c0
 </TASK>
----------------
Code disassembly (best guess):
   0:	14 50                	adc    $0x50,%al
   2:	89 7e 65             	mov    %edi,0x65(%rsi)
   5:	8b 15 15 50 89 7e    	mov    0x7e895015(%rip),%edx        # 0x7e895020
   b:	81 e2 00 01 ff 00    	and    $0xff0100,%edx
  11:	74 11                	je     0x24
  13:	81 fa 00 01 00 00    	cmp    $0x100,%edx
  19:	75 35                	jne    0x50
  1b:	83 b9 34 16 00 00 00 	cmpl   $0x0,0x1634(%rcx)
  22:	74 2c                	je     0x50
  24:	8b 91 10 16 00 00    	mov    0x1610(%rcx),%edx
* 2a:	83 fa 02             	cmp    $0x2,%edx <-- trapping instruction
  2d:	75 21                	jne    0x50
  2f:	48 8b 91 18 16 00 00 	mov    0x1618(%rcx),%rdx
  36:	48 8b 32             	mov    (%rdx),%rsi
  39:	48 8d 7e 01          	lea    0x1(%rsi),%rdi
  3d:	8b                   	.byte 0x8b
  3e:	89                   	.byte 0x89
  3f:	14                   	.byte 0x14