==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88812fcac590 by task syz.4.1675/4590
CPU: 1 PID: 4590 Comm: syz.4.1675 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
__dump_stack+0x21/0x30 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:427 [inline]
kasan_report+0x10f/0x150 mm/kasan/report.c:444
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
rcu_do_batch+0x47d/0xbf0 kernel/rcu/tree.c:2512
rcu_core+0x4a3/0xef0 kernel/rcu/tree.c:2763
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
handle_softirqs+0x250/0x560 kernel/softirq.c:583
__do_softirq kernel/softirq.c:621 [inline]
invoke_softirq kernel/softirq.c:443 [inline]
__irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670
irq_exit_rcu+0x9/0x10 kernel/softirq.c:682
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__kasan_check_read+0x6/0x20 mm/kasan/shadow.c:31
Code: 5e 41 5f 5d c3 48 c7 c7 83 10 e8 85 eb 0a 48 c7 c7 20 e5 dc 85 48 89 de e8 07 0f 03 03 45 31 ff eb d1 00 00 55 48 89 e5 89 f6 <48> 8b 4d 08 31 d2 e8 af ed ff ff 5d c3 66 2e 0f 1f 84 00 00 00 00
RSP: 0018:ffffc90000cd7890 EFLAGS: 00000282
RAX: 8000000127176007 RBX: 8000000127176007 RCX: ffff888123520000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff888123520000
RBP: ffffc90000cd7890 R08: ffffea000441c273 R09: 1ffffd400088384e
R10: dffffc0000000000 R11: fffff9400088384f R12: 1ffff11037653c52
R13: 00007f7c76a00000 R14: ffff888123520000 R15: 00007f7c76853000
instrument_atomic_read include/linux/instrumented.h:71 [inline]
test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
test_ti_thread_flag include/linux/thread_info.h:118 [inline]
need_resched include/linux/sched.h:2167 [inline]
zap_pte_range mm/memory.c:1418 [inline]
zap_pmd_range mm/memory.c:1577 [inline]
zap_pud_range mm/memory.c:1606 [inline]
zap_p4d_range mm/memory.c:1627 [inline]
unmap_page_range+0xacc/0x1e00 mm/memory.c:1648
unmap_single_vma mm/memory.c:1693 [inline]
unmap_vmas+0x26d/0x380 mm/memory.c:1725
exit_mmap+0x412/0x8b0 mm/mmap.c:3245
__mmput+0x92/0x300 kernel/fork.c:1191
mmput+0x50/0x150 kernel/fork.c:1214
exit_mm kernel/exit.c:561 [inline]
do_exit+0xacc/0x29a0 kernel/exit.c:883
do_group_exit+0x149/0x310 kernel/exit.c:1010
__do_sys_exit_group kernel/exit.c:1021 [inline]
__se_sys_exit_group kernel/exit.c:1019 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1019
x64_sys_call+0x832/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
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: 0033:0x7f7c777c4559
Code: Unable to access opcode bytes at RIP 0x7f7c777c452f.
RSP: 002b:00007fff284b30c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7c777c4559
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fff284b312c R08: 0000000000000000 R09: 00000000000927c0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000053
R13: 00000000000927c0 R14: 00000000000245e0 R15: 00007fff284b3180
Allocated by task 4581:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:433 [inline]
____kasan_kmalloc mm/kasan/common.c:512 [inline]
__kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:521
kasan_kmalloc include/linux/kasan.h:227 [inline]
__kmalloc+0x13d/0x2c0 mm/slub.c:4436
kmalloc include/linux/slab.h:624 [inline]
kzalloc include/linux/slab.h:750 [inline]
l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
__sys_connect_file net/socket.c:1923 [inline]
__sys_connect+0x3cb/0x450 net/socket.c:1940
__do_sys_connect net/socket.c:1950 [inline]
__se_sys_connect net/socket.c:1947 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:1947
x64_sys_call+0x7c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
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 8:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
kasan_slab_free include/linux/kasan.h:193 [inline]
slab_free_hook mm/slub.c:1728 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
slab_free mm/slub.c:3526 [inline]
kfree+0xc4/0x270 mm/slub.c:4588
l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193
l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline]
l2tp_tunnel_del_work+0x180/0x3d0 net/l2tp/l2tp_core.c:1273
process_one_work+0x6c8/0xbb0 kernel/workqueue.c:2328
worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475
kthread+0x3f5/0x4f0 kernel/kthread.c:337
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
Last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
__call_rcu_common kernel/rcu/tree.c:3011 [inline]
call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
__sock_release net/socket.c:649 [inline]
sock_close+0xb8/0x200 net/socket.c:1336
__fput+0x22b/0x900 fs/file_table.c:311
____fput+0x15/0x20 fs/file_table.c:339
task_work_run+0x127/0x190 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:184
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:217
__syscall_exit_to_user_mode_work kernel/entry/common.c:299 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:310
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
The buggy address belongs to the object at ffff88812fcac400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88812fcac400, ffff88812fcac600)
The buggy address belongs to the page:
page:ffffea0004bf2b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12fcac
head:ffffea0004bf2b00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100042f00
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 45, ts 29405353666, free_ts 27834471521
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2610
prep_new_page+0x1c/0x110 mm/page_alloc.c:2616
get_page_from_freelist+0x2d42/0x2dd0 mm/page_alloc.c:4492
__alloc_pages+0x1a2/0x460 mm/page_alloc.c:5829
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1937 [inline]
new_slab+0xa0/0x4d0 mm/slub.c:2000
___slab_alloc+0x3ac/0x840 mm/slub.c:3033
__slab_alloc+0x49/0x90 mm/slub.c:3120
slab_alloc_node mm/slub.c:3211 [inline]
slab_alloc mm/slub.c:3255 [inline]
__kmalloc+0x16a/0x2c0 mm/slub.c:4432
kmalloc include/linux/slab.h:624 [inline]
kzalloc include/linux/slab.h:750 [inline]
fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:155
ip6_route_info_create+0x51b/0x14d0 net/ipv6/route.c:3787
addrconf_f6i_alloc+0x19c/0x3f0 net/ipv6/route.c:4587
ipv6_add_addr+0x442/0xd90 net/ipv6/addrconf.c:1125
addrconf_add_linklocal+0x209/0x660 net/ipv6/addrconf.c:3280
addrconf_addr_gen+0x53f/0x6a0 net/ipv6/addrconf.c:3411
addrconf_dev_config net/ipv6/addrconf.c:3456 [inline]
addrconf_init_auto_addrs+0x867/0xbd0 net/ipv6/addrconf.c:3535
addrconf_notify+0x95d/0xe00 net/ipv6/addrconf.c:3704
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1477 [inline]
free_pcp_prepare mm/page_alloc.c:1549 [inline]
free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3540
free_unref_page_list+0x138/0x9e0 mm/page_alloc.c:3677
release_pages+0x1264/0x12c0 mm/swap.c:1033
__pagevec_release+0x71/0xe0 mm/swap.c:1053
pagevec_release include/linux/pagevec.h:81 [inline]
shmem_undo_range+0x564/0x13b0 mm/shmem.c:965
shmem_truncate_range mm/shmem.c:1064 [inline]
shmem_evict_inode+0x1dc/0x970 mm/shmem.c:1146
evict+0x4b6/0x8b0 fs/inode.c:650
iput_final fs/inode.c:1779 [inline]
iput+0x651/0x7e0 fs/inode.c:1805
do_unlinkat+0x380/0x6c0 fs/namei.c:4363
__do_sys_unlink fs/namei.c:4404 [inline]
__se_sys_unlink fs/namei.c:4402 [inline]
__x64_sys_unlink+0x49/0x50 fs/namei.c:4402
x64_sys_call+0x878/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:88
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:
ffff88812fcac480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88812fcac500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88812fcac580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88812fcac600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88812fcac680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 5e pop %rsi
1: 41 5f pop %r15
3: 5d pop %rbp
4: c3 ret
5: 48 c7 c7 83 10 e8 85 mov $0xffffffff85e81083,%rdi
c: eb 0a jmp 0x18
e: 48 c7 c7 20 e5 dc 85 mov $0xffffffff85dce520,%rdi
15: 48 89 de mov %rbx,%rsi
18: e8 07 0f 03 03 call 0x3030f24
1d: 45 31 ff xor %r15d,%r15d
20: eb d1 jmp 0xfffffff3
22: 00 00 add %al,(%rax)
24: 55 push %rbp
25: 48 89 e5 mov %rsp,%rbp
28: 89 f6 mov %esi,%esi
* 2a: 48 8b 4d 08 mov 0x8(%rbp),%rcx <-- trapping instruction
2e: 31 d2 xor %edx,%edx
30: e8 af ed ff ff call 0xffffede4
35: 5d pop %rbp
36: c3 ret
37: 66 data16
38: 2e cs
39: 0f .byte 0xf
3a: 1f (bad)
3b: 84 00 test %al,(%rax)
3d: 00 00 add %al,(%rax)