=============================
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.4.753/8440:
#0: ffff8880257980e0 (&type->s_umount_key#102/1){+.+.}-{3:3}, at: alloc_super+0x201/0x950 fs/super.c:229
#1: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#2: ffff8880243e3948 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6d9/0x880 net/core/dev.c:5154
#3: ffff8880243e3908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#3: ffff8880243e3908 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x311/0x4b0 net/sched/sch_generic.c:357
#4: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 0 PID: 8440 Comm: syz.4.753 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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:make_kgid+0x1/0x660 kernel/user_namespace.c:472
Code: 49 00 e9 a6 fd ff ff 44 89 e1 80 e1 07 80 c1 03 38 c1 0f 8c e3 fd ff ff 4c 89 e7 e8 49 23 49 00 e9 d6 fd ff ff 0f 1f 40 00 55 <48> 89 e5 41 57 41 56 41 55 41 54 53 48 83 e4 e0 48 81 ec 80 00 00
RSP: 0000:ffffc9000344f890 EFLAGS: 00000246
RAX: ffffffff837126a1 RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000e9a9000 RSI: 0000000000000000 RDI: ffffffff8c1cc840
RBP: ffffc9000344fa10 R08: ffffea0001968377 R09: 1ffffd400032d06e
R10: dffffc0000000000 R11: fffff9400032d06f R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000009e51
make_kqid include/linux/quota.h:108 [inline]
gfs2_quota_init+0x6c0/0xea0 fs/gfs2/quota.c:1419
gfs2_make_fs_rw+0x414/0x580 fs/gfs2/super.c:159
gfs2_fill_super+0x1837/0x1f00 fs/gfs2/ops_fstype.c:1276
get_tree_bdev+0x3f1/0x610 fs/super.c:1325
gfs2_get_tree+0x4d/0x1e0 fs/gfs2/ops_fstype.c:1332
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: 0033:0x7f77a7c2004a
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:00007f77a5e56e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f77a5e56ee0 RCX: 00007f77a7c2004a
RDX: 00002000000124c0 RSI: 0000200000012500 RDI: 00007f77a5e56ea0
RBP: 00002000000124c0 R08: 00007f77a5e56ee0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000012500
R13: 00007f77a5e56ea0 R14: 00000000000125c7 R15: 0000200000000180
----------------
Code disassembly (best guess), 2 bytes skipped:
0: e9 a6 fd ff ff jmp 0xfffffdab
5: 44 89 e1 mov %r12d,%ecx
8: 80 e1 07 and $0x7,%cl
b: 80 c1 03 add $0x3,%cl
e: 38 c1 cmp %al,%cl
10: 0f 8c e3 fd ff ff jl 0xfffffdf9
16: 4c 89 e7 mov %r12,%rdi
19: e8 49 23 49 00 call 0x492367
1e: e9 d6 fd ff ff jmp 0xfffffdf9
23: 0f 1f 40 00 nopl 0x0(%rax)
27: 55 push %rbp
* 28: 48 89 e5 mov %rsp,%rbp <-- trapping instruction
2b: 41 57 push %r15
2d: 41 56 push %r14
2f: 41 55 push %r13
31: 41 54 push %r12
33: 53 push %rbx
34: 48 83 e4 e0 and $0xffffffffffffffe0,%rsp
38: 48 rex.W
39: 81 .byte 0x81
3a: ec in (%dx),%al
3b: 80 00 00 addb $0x0,(%rax)