==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff88810f0b3190 by task syz-executor/361
CPU: 1 PID: 361 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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:massage_pgprot arch/x86/include/asm/pgtable.h:552 [inline]
RIP: 0010:check_pgprot arch/x86/include/asm/pgtable.h:559 [inline]
RIP: 0010:pfn_pte arch/x86/include/asm/pgtable.h:579 [inline]
RIP: 0010:do_set_pte+0xce/0x470 mm/memory.c:4322
Code: 75 0a e8 c5 9d ca ff 4c 89 f3 eb 36 e8 bb 9d ca ff 48 c7 c0 f0 5d e9 86 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 <74> 0c 48 c7 c7 f0 5d e9 86 e8 34 1e 0a 00 48 8b 1d 3d 20 4a 05 4c
RSP: 0000:ffffc9000835f7c0 EFLAGS: 00000246
RAX: 1ffffffff0dd2bbe RBX: dffffc0000000000 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000835f810 R08: ffffea00045bb147 R09: 1ffffd40008b7628
R10: dffffc0000000000 R11: fffff940008b7629 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000025 R15: ffff88812aa1ede0
filemap_map_pages+0x64a/0x1630 mm/filemap.c:3442
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]
do_user_addr_fault+0x808/0x11c0 arch/x86/mm/fault.c:1416
handle_page_fault arch/x86/mm/fault.c:1507 [inline]
exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1560
asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7fa5d06de1c0
Code: Unable to access opcode bytes at RIP 0x7fa5d06de196.
RSP: 002b:00007fff860c2508 EFLAGS: 00010202
RAX: 00007fa5d07659af RBX: 00007fff860c2a40 RCX: 0000000000000000
RDX: 0000000000000016 RSI: 00007fa5d0765999 RDI: 00007fff860c2a40
RBP: 00007fa5d07659af R08: 00007fff860c2cb0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 0000000000000000 R14: 00007fa5d0765999 R15: 00007fff860c2b00
Allocated by task 356:
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 306:
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 ffff88810f0b3000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff88810f0b3000, ffff88810f0b3200)
The buggy address belongs to the page:
page:ffffea00043c2c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10f0b0
head:ffffea00043c2c00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100042f00
raw: 0000000000000000 0000000000100010 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 105, ts 5619086446, free_ts 0
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_track_caller+0x169/0x2c0 mm/slub.c:4954
kmalloc_reserve net/core/skbuff.c:357 [inline]
__alloc_skb+0x210/0x730 net/core/skbuff.c:428
alloc_skb include/linux/skbuff.h:1183 [inline]
alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6223
sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2541
unix_dgram_sendmsg+0x6f3/0x19b0 net/unix/af_unix.c:1816
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
sock_write_iter+0x2a6/0x3a0 net/socket.c:1080
call_write_iter include/linux/fs.h:2218 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x831/0xfd0 fs/read_write.c:594
ksys_write+0x14a/0x260 fs/read_write.c:647
__do_sys_write fs/read_write.c:659 [inline]
__se_sys_write fs/read_write.c:656 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:656
page_owner free stack trace missing
Memory state around the buggy address:
ffff88810f0b3080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88810f0b3100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810f0b3180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88810f0b3200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88810f0b3280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 75 0a jne 0xc
2: e8 c5 9d ca ff call 0xffca9dcc
7: 4c 89 f3 mov %r14,%rbx
a: eb 36 jmp 0x42
c: e8 bb 9d ca ff call 0xffca9dcc
11: 48 c7 c0 f0 5d e9 86 mov $0xffffffff86e95df0,%rax
18: 48 c1 e8 03 shr $0x3,%rax
1c: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
23: fc ff df
26: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1)
* 2a: 74 0c je 0x38 <-- trapping instruction
2c: 48 c7 c7 f0 5d e9 86 mov $0xffffffff86e95df0,%rdi
33: e8 34 1e 0a 00 call 0xa1e6c
38: 48 8b 1d 3d 20 4a 05 mov 0x54a203d(%rip),%rbx # 0x54a207c
3f: 4c rex.WR