==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff8881297a1990 by task syz.3.107/757
CPU: 0 PID: 757 Comm: syz.3.107 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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:shmem_add_to_page_cache+0x9f/0xc50 mm/shmem.c:703
Code: f8 f8 f8 f8 4b 89 04 37 48 b8 f8 f8 f3 f3 f3 f3 f3 f3 4b 89 44 37 08 e8 9f 7f d1 ff 43 c7 44 37 04 00 00 00 00 4c 89 7c 24 28 <66> 43 c7 44 37 08 00 00 48 8d bc 24 90 00 00 00 ba 20 00 00 00 31
RSP: 0018:ffffc90000b77780 EFLAGS: 00000246
RAX: ffffffff81983741 RBX: ffffea0004d29f80 RCX: 0000000000080000
RDX: ffffc90002760000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc90000b778b8 R08: 0000000000000cc0 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff940009a53f1 R12: ffff88810ded85d0
R13: 0000000000000fd9 R14: dffffc0000000000 R15: 1ffff9200016eefc
shmem_getpage_gfp+0x1404/0x2250 mm/shmem.c:1942
shmem_getpage mm/shmem.c:152 [inline]
shmem_write_begin+0xce/0x1b0 mm/shmem.c:2476
generic_perform_write+0x2b7/0x690 mm/filemap.c:3887
__generic_file_write_iter+0x268/0x490 mm/filemap.c:4015
generic_file_write_iter+0xa9/0x1d0 mm/filemap.c:4047
call_write_iter include/linux/fs.h:2212 [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
x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
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: 0033:0x7f2defa1f019
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:00007f2dee478028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2defca6fa0 RCX: 00007f2defa1f019
RDX: 00000000fffffdab RSI: 0000200000000000 RDI: 0000000000000005
RBP: 00007f2defab600c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2defca7038 R14: 00007f2defca6fa0 R15: 00007ffe6b9fe2c8
Allocated by task 760:
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: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 ffff8881297a1800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
512-byte region [ffff8881297a1800, ffff8881297a1a00)
The buggy address belongs to the page:
page:ffffea0004a5e800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1297a0
head:ffffea0004a5e800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004a5e700 0000000400000004 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 285, ts 23793762199, 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]
kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272
kmalloc include/linux/slab.h:619 [inline]
kmalloc_array include/linux/slab.h:658 [inline]
rtnl_newlink+0x17f/0x1900 net/core/rtnetlink.c:3572
rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5654
netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2516
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5672
netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1348
netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1927
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
__sys_sendto+0x46d/0x620 net/socket.c:2063
__do_sys_sendto net/socket.c:2075 [inline]
__se_sys_sendto net/socket.c:2071 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2071
page_owner free stack trace missing
Memory state around the buggy address:
ffff8881297a1880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881297a1900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881297a1980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881297a1a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881297a1a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: f8 clc
1: f8 clc
2: f8 clc
3: f8 clc
4: 4b 89 04 37 mov %rax,(%r15,%r14,1)
8: 48 b8 f8 f8 f3 f3 f3 movabs $0xf3f3f3f3f3f3f8f8,%rax
f: f3 f3 f3
12: 4b 89 44 37 08 mov %rax,0x8(%r15,%r14,1)
17: e8 9f 7f d1 ff call 0xffd17fbb
1c: 43 c7 44 37 04 00 00 movl $0x0,0x4(%r15,%r14,1)
23: 00 00
25: 4c 89 7c 24 28 mov %r15,0x28(%rsp)
* 2a: 66 43 c7 44 37 08 00 movw $0x0,0x8(%r15,%r14,1) <-- trapping instruction
31: 00
32: 48 8d bc 24 90 00 00 lea 0x90(%rsp),%rdi
39: 00
3a: ba 20 00 00 00 mov $0x20,%edx
3f: 31 .byte 0x31