syzbot
KASAN: slab-use-after-free Read in ring_buffer_lock_reserve
Status:
moderation: reported on 2026/09/25 00:28
Subsystems:
trace
Labels:
prio:normal
[Documentation on labels]
Reported-by: syzbot+447b407e06b77853194d@syzkaller.appspotmail.com
First crash: 4d01h, last: 4d01h
Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in rb_is_reader_page kernel/trace/ring_buffer.c:1353 [inline]
BUG: KASAN: slab-use-after-free in rb_move_tail+0x1653/0x19e0 kernel/trace/ring_buffer.c:3964
Read of size 8 at addr ffff888033712280 by task syz-executor/6764
CPU: 0 UID: 0 PID: 6764 Comm: syz-executor Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2026
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x13d/0x4b0 mm/kasan/report.c:482
kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
rb_is_reader_page kernel/trace/ring_buffer.c:1353 [inline]
rb_move_tail+0x1653/0x19e0 kernel/trace/ring_buffer.c:3964
__rb_reserve_next.constprop.0+0x8cf/0x1640 kernel/trace/ring_buffer.c:4854
rb_reserve_next_event kernel/trace/ring_buffer.c:5010 [inline]
ring_buffer_lock_reserve+0x49a/0x1220 kernel/trace/ring_buffer.c:5069
__trace_buffer_lock_reserve kernel/trace/trace.h:1677 [inline]
trace_event_buffer_lock_reserve+0x123/0x6f0 kernel/trace/trace.c:1924
trace_event_buffer_reserve+0x1f9/0x350 kernel/trace/trace_events.c:715
do_trace_event_raw_event_lock include/trace/events/lock.h:49 [inline]
trace_event_raw_event_lock+0x124/0x2b0 include/trace/events/lock.h:49
__do_trace_lock_release include/trace/events/lock.h:68 [inline]
trace_lock_release include/trace/events/lock.h:68 [inline]
lock_release+0x218/0x310 kernel/locking/lockdep.c:5954
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:208 [inline]
_raw_spin_unlock_irqrestore+0x1a/0x80 kernel/locking/spinlock.c:221
debug_object_activate+0x343/0x4b0 lib/debugobjects.c:891
debug_hrtimer_activate kernel/time/hrtimer.c:486 [inline]
debug_activate kernel/time/hrtimer.c:529 [inline]
enqueue_hrtimer+0x75/0x2f0 kernel/time/hrtimer.c:1136
__run_hrtimer kernel/time/hrtimer.c:2090 [inline]
__hrtimer_run_queues+0x6ed/0x9c0 kernel/time/hrtimer.c:2131
hrtimer_interrupt+0x441/0xaa0 kernel/time/hrtimer.c:2250
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x109/0x470 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0x51/0xc0 arch/x86/kernel/apic/apic.c:1062
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:in_softirq_really kernel/kcov.c:167 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:179 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x27/0x70 kernel/kcov.c:213
Code: 90 90 90 f3 0f 1e fa 65 48 8b 05 6c 80 80 12 48 8b 34 24 65 48 8b 15 50 80 80 12 48 63 c8 a9 00 01 00 ff 74 1e f6 c4 01 74 44 <a9> 00 00 00 0f 75 3d f7 c1 00 00 00 f0 75 35 8b 82 3c 17 00 00 85
RSP: 0018:ffffc90000007c80 EFLAGS: 00000202
RAX: 0000000000000104 RBX: ffffc90000007d00 RCX: 0000000000000104
RDX: ffff88802e8e4b00 RSI: ffffffff821554d0 RDI: ffffc90000007d00
RBP: ffff88801d29d600 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffffffff8edec4a0
R13: 0000000000000026 R14: ffffffff8bf19b80 R15: ffff88801d29d600
trace_event_buffer_reserve+0x20/0x350 kernel/trace/trace_events.c:699
do_trace_event_raw_event_lock include/trace/events/lock.h:49 [inline]
trace_event_raw_event_lock+0x124/0x2b0 include/trace/events/lock.h:49
__do_trace_lock_release include/trace/events/lock.h:68 [inline]
trace_lock_release include/trace/events/lock.h:68 [inline]
lock_release+0x218/0x310 kernel/locking/lockdep.c:5954
rcu_lock_release include/linux/rcupdate.h:319 [inline]
rcu_read_unlock include/linux/rcupdate.h:880 [inline]
taprio_dequeue+0x161/0x5f0 net/sched/sch_taprio.c:868
dequeue_skb net/sched/sch_generic.c:322 [inline]
qdisc_restart net/sched/sch_generic.c:427 [inline]
__qdisc_run+0x1be/0x1b20 net/sched/sch_generic.c:445
qdisc_run include/net/pkt_sched.h:121 [inline]
qdisc_run include/net/pkt_sched.h:118 [inline]
net_tx_action+0x549/0xf50 net/core/dev.c:5915
handle_softirqs+0x1e6/0x9d0 kernel/softirq.c:645
__do_softirq kernel/softirq.c:679 [inline]
invoke_softirq kernel/softirq.c:519 [inline]
__irq_exit_rcu+0x16a/0x210 kernel/softirq.c:758
irq_exit_rcu+0x9/0x30 kernel/softirq.c:775
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:__rb_reserve_next.constprop.0+0x394/0x1640 kernel/trace/ring_buffer.c:4859
Code: 89 ff e8 8f 2b fd ff 4d 39 e7 0f 85 c4 07 00 00 e8 a1 31 fd ff 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 <0f> 85 f5 0f 00 00 4c 8b 7c 24 28 be 08 00 00 00 4c 8b 23 4c 89 ff
RSP: 0018:ffffc90005f1f3e8 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: ffffc90005f1f530 RCX: 0000000000000002
RDX: 1ffff92000be3ea6 RSI: ffffffff820eee0f RDI: ffff88802e8e4b00
RBP: ffff88801c095000 R08: 0000000000000006 R09: 0000000000000228
R10: 0000000000000228 R11: 0000000000000000 R12: 0000000000000228
R13: ffff88801c095150 R14: ffff88801c08c680 R15: 0000000000000228
rb_reserve_next_event kernel/trace/ring_buffer.c:5010 [inline]
ring_buffer_lock_reserve+0x49a/0x1220 kernel/trace/ring_buffer.c:5069
__trace_buffer_lock_reserve kernel/trace/trace.h:1677 [inline]
trace_event_buffer_lock_reserve+0x123/0x6f0 kernel/trace/trace.c:1924
trace_event_buffer_reserve+0x1f9/0x350 kernel/trace/trace_events.c:715
do_trace_event_raw_event_lock include/trace/events/lock.h:49 [inline]
trace_event_raw_event_lock+0x124/0x2b0 include/trace/events/lock.h:49
__do_trace_lock_release include/trace/events/lock.h:68 [inline]
trace_lock_release include/trace/events/lock.h:68 [inline]
lock_release+0x218/0x310 kernel/locking/lockdep.c:5954
might_alloc include/linux/sched/mm.h:316 [inline]
slab_pre_alloc_hook mm/slub.c:4636 [inline]
slab_alloc_node mm/slub.c:4974 [inline]
kmem_cache_alloc_noprof+0x63/0x6a0 mm/slub.c:5010
anon_vma_alloc mm/rmap.c:94 [inline]
anon_vma_fork+0x8d/0x6a0 mm/rmap.c:391
dup_mmap+0x10e6/0x2370 mm/mmap.c:1781
dup_mm kernel/fork.c:1543 [inline]
copy_mm kernel/fork.c:1595 [inline]
copy_process+0x4811/0x8370 kernel/fork.c:2310
kernel_clone+0x176/0x9d0 kernel/fork.c:2769
__do_sys_clone+0xd9/0x120 kernel/fork.c:2911
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f122a9c6bd2
Code: 89 e7 e8 71 8b f7 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 66 89 c5 85 c0 75 3b 64 48 8b 04 25 10 00 00
RSP: 002b:00007fffda742550 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fffda742550 RCX: 00007f122a9c6bd2
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007fffda7426dc R08: 0000000000000000 R09: 0000000000000001
R10: 000055557d0397d0 R11: 0000000000000246 R12: 0000000000000001
R13: 000055557d04ca10 R14: 000000000008d88f R15: 00007fffda742730
</TASK>
Allocated by task 6453:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5414 [inline]
__kmalloc_node_noprof+0x342/0x880 mm/slub.c:5426
_kmalloc_node_noprof include/linux/slab.h:1200 [inline]
__rb_allocate_pages+0x308/0xfc0 kernel/trace/ring_buffer.c:2483
ring_buffer_resize+0x71c/0x1ed0 kernel/trace/ring_buffer.c:3357
__tracing_resize_ring_buffer.part.0+0x52/0x1f0 kernel/trace/trace.c:4740
__tracing_resize_ring_buffer kernel/trace/trace.c:4734 [inline]
tracing_update_buffers+0xd4/0xf0 kernel/trace/trace.c:4979
ftrace_event_write+0x14a/0x2c0 kernel/trace/trace_events.c:1562
vfs_write+0x2aa/0x1050 fs/read_write.c:685
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 10552:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2748 [inline]
slab_free mm/slub.c:6508 [inline]
kfree+0x22b/0x6d0 mm/slub.c:6801
free_buffer_page kernel/trace/ring_buffer.c:418 [inline]
rb_remove_pages kernel/trace/ring_buffer.c:3169 [inline]
rb_update_pages+0x675/0xd60 kernel/trace/ring_buffer.c:3268
update_pages_handler kernel/trace/ring_buffer.c:3279 [inline]
ring_buffer_resize+0x14af/0x1ed0 kernel/trace/ring_buffer.c:3389
__tracing_resize_ring_buffer.part.0+0x52/0x1f0 kernel/trace/trace.c:4740
__tracing_resize_ring_buffer kernel/trace/trace.c:4734 [inline]
tracing_resize_ring_buffer+0x10b/0x160 kernel/trace/trace.c:4795
tracing_entries_write+0x15d/0x220 kernel/trace/trace.c:5741
do_loop_readv_writev fs/read_write.c:851 [inline]
do_loop_readv_writev fs/read_write.c:836 [inline]
vfs_writev+0x5ed/0xdd0 fs/read_write.c:1060
do_writev+0x13e/0x340 fs/read_write.c:1104
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888033712280
which belongs to the cache kmalloc-64 of size 64
The buggy address is located 0 bytes inside of
freed 64-byte region [ffff888033712280, ffff8880337122c0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x33712
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801c0348c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000200020 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 12447819587
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
prep_new_page mm/page_alloc.c:1879 [inline]
get_page_from_freelist+0x110d/0x35d0 mm/page_alloc.c:3943
__alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
alloc_slab_page mm/slub.c:3347 [inline]
allocate_slab mm/slub.c:3462 [inline]
new_slab+0xa9/0x6e0 mm/slub.c:3513
refill_objects+0xe3/0x410 mm/slub.c:7417
refill_sheaf mm/slub.c:2885 [inline]
__pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4774
alloc_from_pcs mm/slub.c:4850 [inline]
slab_alloc_node mm/slub.c:4984 [inline]
__do_kmalloc_node mm/slub.c:5413 [inline]
__kmalloc_noprof+0x67c/0x840 mm/slub.c:5439
_kmalloc_noprof include/linux/slab.h:995 [inline]
_kzalloc_noprof include/linux/slab.h:1312 [inline]
handler_new_ref+0x1ab/0xc60 drivers/media/v4l2-core/v4l2-ctrls-core.c:1959
v4l2_ctrl_add_handler drivers/media/v4l2-core/v4l2-ctrls-core.c:2520 [inline]
v4l2_ctrl_add_handler+0x223/0x300 drivers/media/v4l2-core/v4l2-ctrls-core.c:2494
vivid_create_controls+0x33bd/0x3e80 drivers/media/test-drivers/vivid/vivid-ctrls.c:2071
vivid_create_instance drivers/media/test-drivers/vivid/vivid-core.c:1933 [inline]
vivid_probe.cold+0x4f1e/0x921e drivers/media/test-drivers/vivid/vivid-core.c:2095
platform_probe+0x106/0x1d0 drivers/base/platform.c:1507
call_driver_probe drivers/base/dd.c:628 [inline]
really_probe+0x241/0xa60 drivers/base/dd.c:706
__driver_probe_device+0x210/0x460 drivers/base/dd.c:868
driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
__driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
page_owner free stack trace missing
Memory state around the buggy address:
ffff888033712180: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888033712200: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888033712280: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff888033712300: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
ffff888033712380: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 90 nop
1: 90 nop
2: 90 nop
3: f3 0f 1e fa endbr64
7: 65 48 8b 05 6c 80 80 mov %gs:0x1280806c(%rip),%rax # 0x1280807b
e: 12
f: 48 8b 34 24 mov (%rsp),%rsi
13: 65 48 8b 15 50 80 80 mov %gs:0x12808050(%rip),%rdx # 0x1280806b
1a: 12
1b: 48 63 c8 movslq %eax,%rcx
1e: a9 00 01 00 ff test $0xff000100,%eax
23: 74 1e je 0x43
25: f6 c4 01 test $0x1,%ah
28: 74 44 je 0x6e
* 2a: a9 00 00 00 0f test $0xf000000,%eax <-- trapping instruction
2f: 75 3d jne 0x6e
31: f7 c1 00 00 00 f0 test $0xf0000000,%ecx
37: 75 35 jne 0x6e
39: 8b 82 3c 17 00 00 mov 0x173c(%rdx),%eax
3f: 85 .byte 0x85
Struck through repros no longer work on HEAD.