syzbot
KASAN: use-after-free Read in rcu_cblist_dequeue
Status:
upstream: reported on 2026/10/19 19:18
Reported-by: syzbot+c5277dfef51b128c8a76@syzkaller.appspotmail.com
First crash: 4d10h, last: 4d10h
Sample crash report:
==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x68/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff8880242afb08 by task syz-executor/4173
CPU: 0 PID: 4173 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
<IRQ>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
rcu_cblist_dequeue+0x68/0xb0 kernel/rcu/rcu_segcblist.c:75
rcu_do_batch kernel/rcu/tree.c:2510 [inline]
rcu_core+0x87a/0x1650 kernel/rcu/tree.c:2763
handle_softirqs+0x336/0x830 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:bytes_is_nonzero mm/kasan/generic.c:84 [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+0x6e/0x290 mm/kasan/generic.c:189
Code: 49 ba 00 00 00 00 00 fc ff df 4f 8d 1c 16 4c 8d 44 3e ff 4d 89 c1 49 c1 e9 03 4b 8d 1c 21 49 89 df 4d 29 df 49 83 ff 10 7f 29 <4d> 85 ff 0f 84 38 01 00 00 4c 89 cb 48 f7 d3 4c 01 f3 41 80 3b 00
RSP: 0018:ffffc90002f0e7d0 EFLAGS: 00000283
RAX: 0000000000000001 RBX: fffffbfff1cd6506 RCX: ffffffff815cef15
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e6b2828
RBP: ffffc90002f0e908 R08: ffffffff8e6b282f R09: 1ffffffff1cd6505
R10: dffffc0000000000 R11: fffffbfff1cd6505 R12: dffffc0000000001
R13: ffffffff8d113ae0 R14: 1ffffffff1cd6505 R15: 0000000000000001
instrument_atomic_read include/linux/instrumented.h:71 [inline]
test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
cpumask_test_cpu include/linux/cpumask.h:344 [inline]
cpu_online include/linux/cpumask.h:895 [inline]
trace_lock_acquire include/trace/events/lock.h:13 [inline]
lock_acquire+0xb5/0x400 kernel/locking/lockdep.c:5708
__down_trylock_console_sem+0x19f/0x1f0 kernel/printk/printk.c:244
console_trylock kernel/printk/printk.c:2575 [inline]
console_trylock_spinning+0x80/0x370 kernel/printk/printk.c:1867
vprintk_emit+0xa7/0x150 kernel/printk/printk.c:2273
_printk+0xda/0x130 kernel/printk/printk.c:2299
nf_log_buf_close+0x51/0xc0 net/netfilter/nf_log.c:305
nf_log_packet+0x446/0x5f0 net/netfilter/nf_log.c:229
nft_log_eval+0x2c0/0x3b0 net/netfilter/nft_log.c:60
expr_call_ops_eval net/netfilter/nf_tables_core.c:198 [inline]
nft_do_chain+0x491/0x14d0 net/netfilter/nf_tables_core.c:238
nft_do_chain_ipv4+0x156/0x220 net/netfilter/nft_chain_filter.c:23
nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
nf_hook_slow+0xb9/0x200 net/netfilter/core.c:584
nf_hook+0x205/0x360 include/linux/netfilter.h:257
__ip_local_out+0x4b7/0x5e0 net/ipv4/ip_output.c:115
ip_local_out net/ipv4/ip_output.c:124 [inline]
__ip_queue_xmit+0x1120/0x1c60 net/ipv4/ip_output.c:538
__tcp_transmit_skb+0x1ca3/0x31e0 net/ipv4/tcp_output.c:1404
tcp_transmit_skb net/ipv4/tcp_output.c:1422 [inline]
tcp_write_xmit+0x1a8d/0x65c0 net/ipv4/tcp_output.c:2718
__tcp_push_pending_frames+0x92/0x250 net/ipv4/tcp_output.c:2903
tcp_sendmsg_locked+0x2bdd/0x3330 net/ipv4/tcp.c:1432
tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1460
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
sock_write_iter+0x2a6/0x3a0 net/socket.c:1090
call_write_iter include/linux/fs.h:2179 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x748/0xd70 fs/read_write.c:594
ksys_write+0x153/0x260 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: 0033:0x7f9db1a306d7
Code: 48 89 fa 4c 89 df e8 a8 56 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffccfd2e580 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000055557a6df500 RCX: 00007f9db1a306d7
RDX: 000000000000a780 RSI: 00007f9dadacc880 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000a780
R13: 000055557a6f6cf0 R14: 00007ffccfd2eb20 R15: 00007f9dadacc880
</TASK>
Allocated by task 16908:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
kmalloc_node include/linux/slab.h:630 [inline]
kzalloc_node include/linux/slab.h:749 [inline]
qdisc_alloc+0x97/0xae0 net/sched/sch_generic.c:892
qdisc_create+0x171/0x11a0 net/sched/sch_api.c:1234
tc_modify_qdisc+0xae1/0x17d0 net/sched/sch_api.c:-1
rtnetlink_rcv_msg+0x7f1/0xf10 net/core/rtnetlink.c:5698
netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
__sys_sendmsg net/socket.c:2529 [inline]
__do_sys_sendmsg net/socket.c:2538 [inline]
__se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536
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
Freed by task 18244:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1710 [inline]
slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
slab_free mm/slub.c:3504 [inline]
kfree+0xef/0x2a0 mm/slub.c:4564
rcu_do_batch kernel/rcu/tree.c:2523 [inline]
rcu_core+0x96e/0x1650 kernel/rcu/tree.c:2763
handle_softirqs+0x336/0x830 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
Last potentially related work creation:
kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
__call_rcu kernel/rcu/tree.c:3011 [inline]
call_rcu+0x189/0x900 kernel/rcu/tree.c:3091
tcf_chain_head_change_item net/sched/cls_api.c:370 [inline]
tcf_chain0_head_change net/sched/cls_api.c:384 [inline]
tcf_chain_tp_insert net/sched/cls_api.c:1659 [inline]
tcf_chain_tp_insert_unique+0x9ab/0xb80 net/sched/cls_api.c:1708
tc_new_tfilter+0x1477/0x18d0 net/sched/cls_api.c:2100
rtnetlink_rcv_msg+0x83c/0xf10 net/core/rtnetlink.c:5689
netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
__sys_sendmsg net/socket.c:2529 [inline]
__do_sys_sendmsg net/socket.c:2538 [inline]
__se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536
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
Second to last potentially related work creation:
kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
__call_rcu kernel/rcu/tree.c:3011 [inline]
call_rcu+0x189/0x900 kernel/rcu/tree.c:3091
notify_and_destroy net/sched/sch_api.c:1014 [inline]
qdisc_graft+0xfce/0x1610 net/sched/sch_api.c:1099
tc_modify_qdisc+0xe6a/0x17d0 net/sched/sch_api.c:1752
rtnetlink_rcv_msg+0x7f1/0xf10 net/core/rtnetlink.c:5698
netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519
netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340
netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
__sys_sendmsg net/socket.c:2529 [inline]
__do_sys_sendmsg net/socket.c:2538 [inline]
__se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536
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
The buggy address belongs to the object at ffff8880242af800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 776 bytes inside of
1024-byte region [ffff8880242af800, ffff8880242afc00)
The buggy address belongs to the page:
page:ffffea000090aa00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x242a8
head:ffffea000090aa00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888017841dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4185, ts 53576068060, free_ts 53572636887
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
__alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
alloc_slab_page mm/slub.c:1780 [inline]
allocate_slab mm/slub.c:1917 [inline]
new_slab+0xc0/0x4b0 mm/slub.c:1980
___slab_alloc+0x807/0xdd0 mm/slub.c:3013
__slab_alloc mm/slub.c:3100 [inline]
slab_alloc_node mm/slub.c:3191 [inline]
__kmalloc_node_track_caller+0x13d/0x3a0 mm/slub.c:4963
kmalloc_reserve net/core/skbuff.c:356 [inline]
__alloc_skb+0x22c/0x750 net/core/skbuff.c:427
alloc_skb include/linux/skbuff.h:1162 [inline]
nlmsg_new include/net/netlink.h:964 [inline]
rtmsg_fib+0xd7/0x440 net/ipv4/fib_semantics.c:551
fib_table_insert+0xd24/0x1b80 net/ipv4/fib_trie.c:1379
fib_magic+0x2ca/0x3b0 net/ipv4/fib_frontend.c:1113
fib_add_ifaddr+0x3e2/0x5c0 net/ipv4/fib_frontend.c:1157
fib_netdev_event+0x35c/0x480 net/ipv4/fib_frontend.c:1495
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:391
call_netdevice_notifiers_extack net/core/dev.c:2074 [inline]
call_netdevice_notifiers net/core/dev.c:2088 [inline]
__dev_notify_flags+0x194/0x300 net/core/dev.c:8918
dev_change_flags+0xda/0x1a0 net/core/dev.c:8956
do_setlink+0xca4/0x29d0 net/core/rtnetlink.c:2793
__rtnl_newlink net/core/rtnetlink.c:3464 [inline]
rtnl_newlink+0x15bb/0x1920 net/core/rtnetlink.c:3586
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
free_slab mm/slub.c:2020 [inline]
discard_slab mm/slub.c:2026 [inline]
__unfreeze_partials+0x188/0x1e0 mm/slub.c:2512
put_cpu_partial+0x12d/0x190 mm/slub.c:2592
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
slab_alloc mm/slub.c:3233 [inline]
kmem_cache_alloc+0x15d/0x280 mm/slub.c:3238
sock_alloc_inode+0x17/0xb0 net/socket.c:305
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x5f/0x210 fs/inode.c:1001
sock_alloc net/socket.c:628 [inline]
__sock_create+0x128/0x910 net/socket.c:1460
sock_create net/socket.c:1552 [inline]
__sys_socket+0xe2/0x170 net/socket.c:1594
__do_sys_socket net/socket.c:1603 [inline]
__se_sys_socket net/socket.c:1601 [inline]
__x64_sys_socket+0x76/0x80 net/socket.c:1601
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
Memory state around the buggy address:
ffff8880242afa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880242afa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880242afb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880242afb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880242afc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 49 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%r10
7: fc ff df
a: 4f 8d 1c 16 lea (%r14,%r10,1),%r11
e: 4c 8d 44 3e ff lea -0x1(%rsi,%rdi,1),%r8
13: 4d 89 c1 mov %r8,%r9
16: 49 c1 e9 03 shr $0x3,%r9
1a: 4b 8d 1c 21 lea (%r9,%r12,1),%rbx
1e: 49 89 df mov %rbx,%r15
21: 4d 29 df sub %r11,%r15
24: 49 83 ff 10 cmp $0x10,%r15
28: 7f 29 jg 0x53
* 2a: 4d 85 ff test %r15,%r15 <-- trapping instruction
2d: 0f 84 38 01 00 00 je 0x16b
33: 4c 89 cb mov %r9,%rbx
36: 48 f7 d3 not %rbx
39: 4c 01 f3 add %r14,%rbx
3c: 41 80 3b 00 cmpb $0x0,(%r11)
* Struck through repros no longer work on HEAD.