=============================
WARNING: suspicious RCU usage
5.15.185-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
6 locks held by syz.9.410/8128:
#0: ffff8880169e6460 (sb_writers#3){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff88802a53d988 (&sb->s_type->i_mutex_key#8){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
#1: ffff88802a53d988 (&sb->s_type->i_mutex_key#8){+.+.}-{3:3}, at: generic_file_write_iter+0x7e/0x1b0 mm/filemap.c:3941
#2: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
#3: ffff888078037148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
#4: ffff888078037108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
#4: ffff888078037108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:354
#5: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
stack backtrace:
CPU: 1 PID: 8128 Comm: syz.9.410 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
qdisc_lookup+0xa6/0x650 net/sched/sch_api.c:304
qdisc_tree_reduce_backlog+0x213/0x4e0 net/sched/sch_api.c:800
cake_dequeue+0x1b8f/0x4aa0 net/sched/sch_cake.c:2189
qdisc_peek_dequeued+0x6e/0x1f0 include/net/sch_generic.h:1115
tbf_dequeue+0x7d/0xce0 net/sched/sch_tbf.c:265
dequeue_skb net/sched/sch_generic.c:292 [inline]
qdisc_restart net/sched/sch_generic.c:397 [inline]
__qdisc_run+0x237/0x1480 net/sched/sch_generic.c:415
qdisc_run+0x103/0x2f0 include/net/pkt_sched.h:132
net_tx_action+0x6bc/0x870 net/core/dev.c:5128
handle_softirqs+0x328/0x820 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x12f/0x220 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: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+0x7b/0x290 mm/kasan/generic.c:189
Code: 5c 37 ff 48 c1 eb 03 4e 8d 14 3b 4d 89 d6 4d 29 ce 49 83 fe 10 7f 26 4d 85 f6 0f 84 39 01 00 00 48 f7 d3 4c 01 db 41 80 39 00 <0f> 85 c1 01 00 00 49 ff c1 48 ff c3 75 ee e9 1c 01 00 00 44 89 cb
RSP: 0018:ffffc9000311f7a0 EFLAGS: 00000246
RAX: ffffffff81a5da01 RBX: ffffffffffffffff RCX: ffffffff81a5da86
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffea0001f1f140
RBP: ffffc9000311f920 R08: dffffc0000000000 R09: fffff940003e3e28
R10: fffff940003e3e29 R11: 1ffffd40003e3e28 R12: ffffc9000311f860
R13: dffffc0000000000 R14: 0000000000000001 R15: dffffc0000000001
instrument_atomic_read include/linux/instrumented.h:71 [inline]
test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
PageSwapBacked include/linux/page-flags.h:371 [inline]
PageSwapCache include/linux/page-flags.h:415 [inline]
shmem_add_to_page_cache+0x9e6/0x14b0 mm/shmem.c:717
shmem_getpage_gfp+0x1793/0x2d40 mm/shmem.c:1940
shmem_getpage mm/shmem.c:151 [inline]
shmem_write_begin+0xcd/0x1a0 mm/shmem.c:2474
generic_perform_write+0x2aa/0x530 mm/filemap.c:3785
__generic_file_write_iter+0x25f/0x4e0 mm/filemap.c:3912
generic_file_write_iter+0xa6/0x1b0 mm/filemap.c:3944
call_write_iter include/linux/fs.h:2172 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x712/0xd00 fs/read_write.c:594
ksys_write+0x14d/0x250 fs/read_write.c:647
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: 0033:0x7fe0e1d513df
Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 f9 92 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 4c 93 02 00 48
RSP: 002b:00007fe0dfbb9df0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000001000000 RCX: 00007fe0e1d513df
RDX: 0000000001000000 RSI: 00007fe0d779a000 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000009600
R10: 0000200000012cc2 R11: 0000000000000293 R12: 0000000000000004
R13: 00007fe0dfbb9ef0 R14: 00007fe0dfbb9eb0 R15: 00007fe0d779a000
----------------
Code disassembly (best guess), 2 bytes skipped:
0: ff 48 c1 decl -0x3f(%rax)
3: eb 03 jmp 0x8
5: 4e 8d 14 3b lea (%rbx,%r15,1),%r10
9: 4d 89 d6 mov %r10,%r14
c: 4d 29 ce sub %r9,%r14
f: 49 83 fe 10 cmp $0x10,%r14
13: 7f 26 jg 0x3b
15: 4d 85 f6 test %r14,%r14
18: 0f 84 39 01 00 00 je 0x157
1e: 48 f7 d3 not %rbx
21: 4c 01 db add %r11,%rbx
24: 41 80 39 00 cmpb $0x0,(%r9)
* 28: 0f 85 c1 01 00 00 jne 0x1ef <-- trapping instruction
2e: 49 ff c1 inc %r9
31: 48 ff c3 inc %rbx
34: 75 ee jne 0x24
36: e9 1c 01 00 00 jmp 0x157
3b: 44 89 cb mov %r9d,%ebx