=============================
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
5 locks held by syz.4.126/4657:
#0: ffff888079b680e0 (&type->s_umount_key#50/1){+.+.}-{3:3}, at: alloc_super+0x201/0x950 fs/super.c:229
#1: ffffffff8c31f360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#2: ffff888075c1f148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6d9/0x880 net/core/dev.c:5154
#3: ffff888075c1f108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#3: ffff888075c1f108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x311/0x4b0 net/sched/sch_generic.c:357
#4: ffffffff8c31f360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 1 PID: 4657 Comm: syz.4.126 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
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
cake_dequeue+0x1bd6/0x4b10 net/sched/sch_cake.c:2205
qdisc_peek_dequeued+0x6e/0x1f0 include/net/sch_generic.h:1125
tbf_dequeue+0x7d/0xce0 net/sched/sch_tbf.c:265
dequeue_skb net/sched/sch_generic.c:295 [inline]
qdisc_restart net/sched/sch_generic.c:400 [inline]
__qdisc_run+0x236/0x1490 net/sched/sch_generic.c:418
qdisc_run+0x103/0x2f0 include/net/pkt_sched.h:131
net_tx_action+0x6d9/0x880 net/core/dev.c:5154
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
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:write_comp_data kernel/kcov.c:227 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x32/0x80 kernel/kcov.c:293
Code: 64 23 89 7e 65 8b 15 65 23 89 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 5b 83 b9 34 16 00 00 00 74 52 8b 91 10 16 00 00 <83> fa 03 75 47 48 8b 91 18 16 00 00 44 8b 89 14 16 00 00 49 c1 e1
RSP: 0018:ffffc900031cf0d8 EFLAGS: 00000246
RAX: ffffffff83ca6f36 RBX: ffff88807d184bd4 RCX: ffff88801e1f0000
RDX: 0000000000000002 RSI: 0000000000000a00 RDI: 0000000000001001
RBP: ffffc900031cf230 R08: ffff88801e1f0000 R09: 0000000000000004
R10: 0000000000000009 R11: 0000000000000002 R12: dffffc0000000000
R13: 1ffff92000639e34 R14: 0000000000000a00 R15: ffff88807d184b40
__blk_queue_split+0x7d6/0x16e0 block/blk-merge.c:346
blk_mq_submit_bio+0x1de/0x1820 block/blk-mq.c:2219
__submit_bio+0x7d1/0x820 block/blk-core.c:917
__submit_bio_noacct_mq block/blk-core.c:997 [inline]
submit_bio_noacct+0x6b0/0x800 block/blk-core.c:1027
submit_bio+0x2c1/0x560 block/blk-core.c:1089
submit_bio_wait+0x127/0x250 block/bio.c:1229
xfs_rw_bdev+0x45d/0x4e0 fs/xfs/xfs_bio_io.c:55
xlog_do_io+0x17a/0x340 fs/xfs/xfs_log_recover.c:147
xlog_bread+0x30/0xc0 fs/xfs/xfs_log_recover.c:178
xlog_rseek_logrec_hdr+0xfb/0x480 fs/xfs/xfs_log_recover.c:794
xlog_find_tail+0x102/0x9f0 fs/xfs/xfs_log_recover.c:1287
xlog_recover+0x48/0x410 fs/xfs/xfs_log_recover.c:3396
xfs_log_mount+0x393/0x6b0 fs/xfs/xfs_log.c:710
xfs_mountfs+0xb37/0x1b30 fs/xfs/xfs_mount.c:765
xfs_fs_fill_super+0x11a4/0x13f0 fs/xfs/xfs_super.c:1684
get_tree_bdev+0x3f1/0x610 fs/super.c:1325
vfs_get_tree+0x88/0x270 fs/super.c:1530
do_new_mount+0x24a/0xa40 fs/namespace.c:3034
do_mount fs/namespace.c:3377 [inline]
__do_sys_mount fs/namespace.c:3585 [inline]
__se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3562
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: 0033:0x7ffa84ae30ca
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007ffa82d3ae58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffa82d3aee0 RCX: 00007ffa84ae30ca
RDX: 0000200000009700 RSI: 0000200000009740 RDI: 00007ffa82d3aea0
RBP: 0000200000009700 R08: 00007ffa82d3aee0 R09: 0000000004000000
R10: 0000000004000000 R11: 0000000000000246 R12: 0000200000009740
R13: 00007ffa82d3aea0 R14: 000000000000975c R15: 0000200000000740
----------------
Code disassembly (best guess):
0: 64 23 89 7e 65 8b 15 and %fs:0x158b657e(%rcx),%ecx
7: 65 23 89 7e 81 e2 00 and %gs:0xe2817e(%rcx),%ecx
e: 01 ff add %edi,%edi
10: 00 74 11 81 add %dh,-0x7f(%rcx,%rdx,1)
14: fa cli
15: 00 01 add %al,(%rcx)
17: 00 00 add %al,(%rax)
19: 75 5b jne 0x76
1b: 83 b9 34 16 00 00 00 cmpl $0x0,0x1634(%rcx)
22: 74 52 je 0x76
24: 8b 91 10 16 00 00 mov 0x1610(%rcx),%edx
* 2a: 83 fa 03 cmp $0x3,%edx <-- trapping instruction
2d: 75 47 jne 0x76
2f: 48 8b 91 18 16 00 00 mov 0x1618(%rcx),%rdx
36: 44 8b 89 14 16 00 00 mov 0x1614(%rcx),%r9d
3d: 49 rex.WB
3e: c1 .byte 0xc1
3f: e1 .byte 0xe1