==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88811b562990 by task syz.0.995/2973
CPU: 1 PID: 2973 Comm: syz.0.995 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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:constant_test_bit arch/x86/include/asm/bitops.h:207 [inline]
RIP: 0010:test_bit include/asm-generic/bitops/instrumented-non-atomic.h:135 [inline]
RIP: 0010:PageHead include/linux/page-flags.h:597 [inline]
RIP: 0010:thp_nr_pages include/linux/huge_mm.h:282 [inline]
RIP: 0010:find_subpage include/linux/pagemap.h:463 [inline]
RIP: 0010:filemap_map_pages+0x468/0x1630 mm/filemap.c:3423
Code: 48 c1 e8 03 48 89 44 24 68 4c 8b bc 24 c8 00 00 00 4c 89 f7 be 08 00 00 00 e8 64 94 18 00 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 <74> 08 4c 89 f7 e8 6e 92 18 00 4c 89 74 24 10 49 8b 36 b8 00 00 01
RSP: 0018:ffffc90000bdf6a0 EFLAGS: 00000246
RAX: 1ffffd400096d858 RBX: ffff888129697ca8 RCX: ffffffff8190941c
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffea0004b6c2c0
RBP: ffffc90000bdf810 R08: ffffea0004b6c2c7 R09: 1ffffd400096d858
R10: dffffc0000000000 R11: fffff9400096d859 R12: dffffc0000000000
R13: 000000000000001f R14: ffffea0004b6c2c0 R15: 0000000000000014
do_fault_around mm/memory.c:4540 [inline]
do_read_fault mm/memory.c:4561 [inline]
do_fault mm/memory.c:4709 [inline]
handle_pte_fault+0x1b77/0x2770 mm/memory.c:4923
__handle_mm_fault mm/memory.c:-1 [inline]
do_handle_mm_fault+0x1b3b/0x1e30 mm/memory.c:5345
handle_mm_fault include/linux/mm.h:1847 [inline]
faultin_page mm/gup.c:976 [inline]
__get_user_pages+0x80e/0x10c0 mm/gup.c:1197
populate_vma_page_range mm/gup.c:1529 [inline]
__mm_populate+0x324/0x470 mm/gup.c:1638
mm_populate include/linux/mm.h:2704 [inline]
vm_mmap_pgoff+0x245/0x410 mm/util.c:560
ksys_mmap_pgoff+0xf6/0x1d0 mm/mmap.c:1647
__do_sys_mmap arch/x86/kernel/sys_x86_64.c:93 [inline]
__se_sys_mmap arch/x86/kernel/sys_x86_64.c:86 [inline]
__x64_sys_mmap+0xfa/0x110 arch/x86/kernel/sys_x86_64.c:86
x64_sys_call+0x83/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:10
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: 0033:0x7f48ac4ece59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f48aaf46028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f48ac774fa0 RCX: 00007f48ac4ece59
RDX: 000000000300000b RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f48ac582e6f R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f48ac775038 R14: 00007f48ac774fa0 R15: 00007fffce009b18
Allocated by task 2971:
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:1922 [inline]
__sys_connect+0x3cb/0x450 net/socket.c:1939
__do_sys_connect net/socket.c:1949 [inline]
__se_sys_connect net/socket.c:1946 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:1946
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 325:
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:1335
__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:181
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
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 ffff88811b562800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88811b562800, ffff88811b562a00)
The buggy address belongs to the page:
page:ffffea00046d5800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11b560
head:ffffea00046d5800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00044c9c00 0000000300000003 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 1641, ts 83763013095, free_ts 75905137776
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
__alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
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:3783
ip6_route_add+0x27/0x130 net/ipv6/route.c:3879
addrconf_add_mroute net/ipv6/addrconf.c:2532 [inline]
addrconf_add_dev+0x385/0x4c0 net/ipv6/addrconf.c:2550
inet6_addr_add+0x1a6/0x9d0 net/ipv6/addrconf.c:2990
inet6_rtm_newaddr+0x6e7/0x9c0 net/ipv6/addrconf.c:4975
rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5654
netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2516
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1474 [inline]
free_pcp_prepare mm/page_alloc.c:1546 [inline]
free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
free_unref_page+0xae/0x540 mm/page_alloc.c:3618
free_the_page mm/page_alloc.c:805 [inline]
__free_pages+0x6c/0x100 mm/page_alloc.c:5900
__free_slab+0xe5/0x1e0 mm/slub.c:2025
free_slab mm/slub.c:2040 [inline]
discard_slab mm/slub.c:2046 [inline]
__unfreeze_partials+0x15a/0x190 mm/slub.c:2532
put_cpu_partial+0xc6/0x120 mm/slub.c:2612
__slab_free+0x1d4/0x290 mm/slub.c:3395
do_slab_free mm/slub.c:3514 [inline]
___cache_free+0x104/0x120 mm/slub.c:3535
qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157
qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:443
kasan_slab_alloc include/linux/kasan.h:217 [inline]
slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
slab_alloc_node mm/slub.c:3245 [inline]
slab_alloc mm/slub.c:3255 [inline]
kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
kmem_cache_zalloc include/linux/slab.h:740 [inline]
__alloc_file+0x28/0x2a0 fs/file_table.c:132
alloc_empty_file+0x97/0x180 fs/file_table.c:181
Memory state around the buggy address:
ffff88811b562880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88811b562900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811b562980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88811b562a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88811b562a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 48 c1 e8 03 shr $0x3,%rax
4: 48 89 44 24 68 mov %rax,0x68(%rsp)
9: 4c 8b bc 24 c8 00 00 mov 0xc8(%rsp),%r15
10: 00
11: 4c 89 f7 mov %r14,%rdi
14: be 08 00 00 00 mov $0x8,%esi
19: e8 64 94 18 00 call 0x189482
1e: 4c 89 f0 mov %r14,%rax
21: 48 c1 e8 03 shr $0x3,%rax
25: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
* 2a: 74 08 je 0x34 <-- trapping instruction
2c: 4c 89 f7 mov %r14,%rdi
2f: e8 6e 92 18 00 call 0x1892a2
34: 4c 89 74 24 10 mov %r14,0x10(%rsp)
39: 49 8b 36 mov (%r14),%rsi
3c: b8 .byte 0xb8
3d: 00 00 add %al,(%rax)
3f: 01 .byte 0x1