==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888126909190 by task syz.0.1868/7322
CPU: 1 PID: 7322 Comm: syz.0.1868 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
__dump_stack+0x21/0x24 lib/dump_stack.c:77
dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:435 [inline]
kasan_report+0x100/0x140 mm/kasan/report.c:452
__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+0x448/0xaf0 kernel/rcu/tree.c:2484
rcu_core+0x50a/0xca0 kernel/rcu/tree.c:2735
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748
__do_softirq+0x255/0x563 kernel/softirq.c:309
asm_call_irq_on_stack+0xf/0x20
__run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
do_softirq_own_stack+0x60/0x80 arch/x86/kernel/irq_64.c:77
invoke_softirq kernel/softirq.c:405 [inline]
__irq_exit_rcu+0x128/0x150 kernel/softirq.c:435
irq_exit_rcu+0x9/0x10 kernel/softirq.c:447
sysvec_apic_timer_interrupt+0xbf/0xe0 arch/x86/kernel/apic/apic.c:1106
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635
RIP: 0010:__kasan_check_read+0x0/0x20 mm/kasan/shadow.c:30
Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 c7 c7 b4 7d bd 85 eb 0a 48 c7 c7 c2 20 b3 85 48 89 de e8 87 06 da 02 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
RSP: 0018:ffffc90000fef708 EFLAGS: 00000246
RAX: ffffffff81903df4 RBX: ffffea0004e802c0 RCX: 0000000000080000
RDX: ffffc90004556000 RSI: 0000000000000008 RDI: ffffea0004e802c0
RBP: ffffc90000fef738 R08: ffffea0004e802c7 R09: 1ffffd40009d0058
R10: dffffc0000000000 R11: fffff940009d0059 R12: dffffc0000000000
R13: 1ffffd40009d0059 R14: ffffea0004e802c0 R15: ffffea0004e802c0
__cancel_dirty_page+0x2f/0x3b0 mm/page-writeback.c:2654
cancel_dirty_page include/linux/mm.h:2009 [inline]
truncate_cleanup_page+0x1bf/0x220 mm/truncate.c:189
truncate_inode_page+0x55/0x70 mm/truncate.c:224
shmem_undo_range+0x696/0x1740 mm/shmem.c:960
shmem_truncate_range mm/shmem.c:1069 [inline]
shmem_evict_inode+0x1dc/0x970 mm/shmem.c:1169
evict+0x4a9/0x940 fs/inode.c:612
iput_final fs/inode.c:1736 [inline]
iput+0x654/0x7e0 fs/inode.c:1762
dentry_unlink_inode+0x2d5/0x390 fs/dcache.c:378
__dentry_kill+0x45b/0x660 fs/dcache.c:583
dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
dput+0x42/0x80 fs/dcache.c:883
__fput+0x4bd/0x730 fs/file_table.c:294
____fput+0x15/0x20 fs/file_table.c:314
task_work_run+0x127/0x190 kernel/task_work.c:189
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fdf36d4090e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007fdf357d8da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007fdf357d96c0 RCX: 00007fdf36d4090e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
R13: 00007fdf357d8ee0 R14: 00007fdf357d8ea0 R15: 00007fdf2d3b9000
Allocated by task 7327:
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:430 [inline]
____kasan_kmalloc mm/kasan/common.c:509 [inline]
__kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
kasan_kmalloc include/linux/kasan.h:254 [inline]
__kmalloc+0x19f/0x330 mm/slub.c:4038
kmalloc include/linux/slab.h:560 [inline]
kzalloc include/linux/slab.h:667 [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:1867 [inline]
__sys_connect+0x3ce/0x450 net/socket.c:1884
__do_sys_connect net/socket.c:1894 [inline]
__se_sys_connect net/socket.c:1891 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:1891
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
Freed by task 7:
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:362
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
kasan_slab_free include/linux/kasan.h:220 [inline]
slab_free_hook mm/slub.c:1600 [inline]
slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
slab_free mm/slub.c:3208 [inline]
kfree+0xc0/0x270 mm/slub.c:4196
l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
l2tp_session_put+0xb2/0x1a0 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+0x6fd/0xbc0 kernel/workqueue.c:2301
worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
kthread+0x324/0x3b0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
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 kernel/rcu/tree.c:2980 [inline]
call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054
pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
__sock_release net/socket.c:597 [inline]
sock_close+0xb8/0x200 net/socket.c:1287
__fput+0x2dc/0x730 fs/file_table.c:281
____fput+0x15/0x20 fs/file_table.c:314
task_work_run+0x127/0x190 kernel/task_work.c:189
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x61/0xcb
Second to 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
insert_work+0x51/0x320 kernel/workqueue.c:1352
__queue_work+0x91f/0xca0 kernel/workqueue.c:1518
queue_work_on+0xe6/0x140 kernel/workqueue.c:1545
queue_work include/linux/workqueue.h:515 [inline]
schedule_work include/linux/workqueue.h:576 [inline]
__bpf_map_put kernel/bpf/syscall.c:508 [inline]
bpf_map_put+0x1cf/0x240 kernel/bpf/syscall.c:514
bpf_map_put_with_uref kernel/bpf/syscall.c:521 [inline]
bpf_map_release+0x118/0x130 kernel/bpf/syscall.c:531
__fput+0x2dc/0x730 fs/file_table.c:281
____fput+0x15/0x20 fs/file_table.c:314
task_work_run+0x127/0x190 kernel/task_work.c:189
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x61/0xcb
The buggy address belongs to the object at ffff888126909000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff888126909000, ffff888126909200)
The buggy address belongs to the page:
page:ffffea00049a4200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x126908
head:ffffea00049a4200 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000100000001 ffff888100043080
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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 281, ts 19128914654, free_ts 0
set_page_owner include/linux/page_owner.h:35 [inline]
post_alloc_hook mm/page_alloc.c:2456 [inline]
prep_new_page+0x176/0x190 mm/page_alloc.c:2462
get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
__alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1813 [inline]
new_slab+0x84/0x3f0 mm/slub.c:1874
new_slab_objects mm/slub.c:2632 [inline]
___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
__slab_alloc+0x63/0xa0 mm/slub.c:2836
slab_alloc_node mm/slub.c:2918 [inline]
slab_alloc mm/slub.c:2960 [inline]
__kmalloc_track_caller+0x1e4/0x310 mm/slub.c:4541
__kmalloc_reserve net/core/skbuff.c:144 [inline]
__alloc_skb+0xdc/0x520 net/core/skbuff.c:212
alloc_skb include/linux/skbuff.h:1126 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1178 [inline]
netlink_sendmsg+0x693/0xb70 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
__sys_sendto+0x467/0x620 net/socket.c:2007
__do_sys_sendto net/socket.c:2019 [inline]
__se_sys_sendto net/socket.c:2015 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2015
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
page_owner free stack trace missing
Memory state around the buggy address:
ffff888126909080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888126909100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888126909180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888126909200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888126909280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 5b pop %rbx
1: 41 5c pop %r12
3: 41 5d pop %r13
5: 41 5e pop %r14
7: 41 5f pop %r15
9: 5d pop %rbp
a: c3 ret
b: 48 c7 c7 b4 7d bd 85 mov $0xffffffff85bd7db4,%rdi
12: eb 0a jmp 0x1e
14: 48 c7 c7 c2 20 b3 85 mov $0xffffffff85b320c2,%rdi
1b: 48 89 de mov %rbx,%rsi
1e: e8 87 06 da 02 call 0x2da06aa
23: 45 31 ff xor %r15d,%r15d
26: eb d1 jmp 0xfffffff9
28: 00 00 add %al,(%rax)
* 2a: 55 push %rbp <-- trapping instruction
2b: 48 89 e5 mov %rsp,%rbp
2e: 89 f6 mov %esi,%esi
30: 48 8b 4d 08 mov 0x8(%rbp),%rcx
34: 31 d2 xor %edx,%edx
36: e8 af ed ff ff call 0xffffedea
3b: 5d pop %rbp
3c: c3 ret
3d: 66 data16
3e: 2e cs
3f: 0f .byte 0xf