==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff88812e0fcc00 by task syz.2.17/375
CPU: 1 PID: 375 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
__dump_stack+0x21/0x24 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x71/0x200 mm/kasan/report.c:316
print_report+0x4a/0x60 mm/kasan/report.c:420
kasan_report+0x122/0x150 mm/kasan/report.c:524
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
pppol2tp_release+0x16c/0x2d0 net/l2tp/l2tp_ppp.c:434
__sock_release net/socket.c:652 [inline]
sock_close+0xf1/0x290 net/socket.c:1389
__fput+0x1fc/0x8f0 fs/file_table.c:320
____fput+0x15/0x20 fs/file_table.c:348
task_work_run+0x1e1/0x250 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f49d399ce59
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:00007ffefddd27d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffefddd28c0 RCX: 00007f49d399ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000075e1 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b33120000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f49d3c15fac R14: 00007f49d3c15fa8 R15: 00007f49d3c15fa0
Allocated by task 375:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_alloc_info+0x25/0x30 mm/kasan/generic.c:505
____kasan_kmalloc mm/kasan/common.c:380 [inline]
__kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389
kasan_kmalloc include/linux/kasan.h:212 [inline]
__do_kmalloc_node mm/slab_common.c:938 [inline]
__kmalloc+0xb1/0x1e0 mm/slab_common.c:951
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
l2tp_session_create+0x38/0xbe0 net/l2tp/l2tp_core.c:1609
pppol2tp_connect+0xbef/0x1620 net/l2tp/l2tp_ppp.c:771
__sys_connect_file net/socket.c:2000 [inline]
__sys_connect+0x3da/0x460 net/socket.c:2017
__do_sys_connect net/socket.c:2027 [inline]
__se_sys_connect net/socket.c:2024 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2024
x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
Freed by task 10:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x31/0x50 mm/kasan/generic.c:516
____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:250
kasan_slab_free include/linux/kasan.h:178 [inline]
slab_free_hook mm/slub.c:1750 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
slab_free mm/slub.c:3712 [inline]
__kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728
kfree+0x6f/0xf0 mm/slab_common.c:990
l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193
l2tp_session_delete+0x3f0/0x4e0 net/l2tp/l2tp_core.c:1582
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1228 [inline]
l2tp_tunnel_del_work+0x1a1/0x410 net/l2tp/l2tp_core.c:1266
process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
worker_thread+0xa29/0x11e0 kernel/workqueue.c:2449
kthread+0x281/0x320 kernel/kthread.c:386
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
The buggy address belongs to the object at ffff88812e0fcc00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
512-byte region [ffff88812e0fcc00, ffff88812e0fce00)
The buggy address belongs to the physical page:
page:ffffea0004b83f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12e0fc
head:ffffea0004b83f00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 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 375, tgid 375 (syz.2.17), ts 30186099526, free_ts 30185752483
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672
prep_new_page+0x1c/0x110 mm/page_alloc.c:2679
get_page_from_freelist+0x2d12/0x2d80 mm/page_alloc.c:4585
__alloc_pages+0x1fa/0x610 mm/page_alloc.c:5929
alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
allocate_slab mm/slub.c:1967 [inline]
new_slab+0x98/0x3d0 mm/slub.c:2020
___slab_alloc+0x6bd/0xb20 mm/slub.c:3177
__slab_alloc+0x5e/0xa0 mm/slub.c:3263
slab_alloc_node mm/slub.c:3348 [inline]
__kmem_cache_alloc_node+0x203/0x2c0 mm/slub.c:3423
__do_kmalloc_node mm/slab_common.c:937 [inline]
__kmalloc+0xa1/0x1e0 mm/slab_common.c:951
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
l2tp_session_create+0x38/0xbe0 net/l2tp/l2tp_core.c:1609
pppol2tp_connect+0xbef/0x1620 net/l2tp/l2tp_ppp.c:771
__sys_connect_file net/socket.c:2000 [inline]
__sys_connect+0x3da/0x460 net/socket.c:2017
__do_sys_connect net/socket.c:2027 [inline]
__se_sys_connect net/socket.c:2024 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2024
x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1580 [inline]
free_pcp_prepare mm/page_alloc.c:1654 [inline]
free_unref_page_prepare+0x7f8/0x800 mm/page_alloc.c:3620
free_unref_page+0x95/0x540 mm/page_alloc.c:3718
free_the_page mm/page_alloc.c:863 [inline]
__free_pages+0x67/0x100 mm/page_alloc.c:6019
free_pages+0x82/0x90 mm/page_alloc.c:6030
__stack_depot_save+0x457/0x480 lib/stackdepot.c:506
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_set_track+0x60/0x70 mm/kasan/common.c:53
kasan_save_alloc_info+0x25/0x30 mm/kasan/generic.c:505
__kasan_slab_alloc+0x72/0x80 mm/kasan/common.c:334
kasan_slab_alloc include/linux/kasan.h:202 [inline]
slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768
slab_alloc_node mm/slub.c:3382 [inline]
kmem_cache_alloc_node+0x181/0x340 mm/slub.c:3429
__alloc_skb+0xea/0x4b0 net/core/skbuff.c:508
alloc_skb include/linux/skbuff.h:1322 [inline]
nlmsg_new include/net/netlink.h:987 [inline]
audit_buffer_alloc kernel/audit.c:1797 [inline]
audit_log_start+0x428/0x8d0 kernel/audit.c:1915
common_lsm_audit+0xd2/0x1730 security/lsm_audit.c:448
slow_avc_audit+0x1c4/0x240 security/selinux/avc.c:804
avc_audit security/selinux/include/avc.h:136 [inline]
avc_has_perm+0x1fb/0x250 security/selinux/avc.c:1201
sock_has_perm security/selinux/hooks.c:4612 [inline]
selinux_socket_connect_helper+0x27d/0x8f0 security/selinux/hooks.c:4835
Memory state around the buggy address:
ffff88812e0fcb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88812e0fcb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88812e0fcc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88812e0fcc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88812e0fcd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 375 at net/l2tp/l2tp_ppp.c:156 pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Modules linked in:
CPU: 0 PID: 375 Comm: syz.2.17 Tainted: G B syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 ac 91 d4 fc be 02 00 00 00 eb 0a e8 a0 91 d4 fc be 01 00 00 00 4c 89 f7 e8 c3 50 cc fd e9 0f ff ff ff e8 89 91 d4 fc <0f> 0b 48 89 df e8 ff 00 00 00 eb bd e8 78 91 d4 fc 4c 89 f7 be 03
RSP: 0018:ffffc90003777c98 EFLAGS: 00010293
RAX: ffffffff849cebf7 RBX: ffff888114cc4000 RCX: ffff888113c3d100
RDX: 0000000000000000 RSI: 0000000011521110 RDI: 000000000c04eb7d
RBP: ffffc90003777cb8 R08: ffffffff87b767e7 R09: 1ffffffff0f6ecfc
R10: dffffc0000000000 R11: fffffbfff0f6ecfd R12: dffffc0000000000
R13: 1ffff1102473687b R14: 0000000011521110 R15: ffff88812e0fcc00
FS: 000055556391b500(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f49d39ea540 CR3: 000000011467a000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
pppol2tp_release+0x16c/0x2d0 net/l2tp/l2tp_ppp.c:434
__sock_release net/socket.c:652 [inline]
sock_close+0xf1/0x290 net/socket.c:1389
__fput+0x1fc/0x8f0 fs/file_table.c:320
____fput+0x15/0x20 fs/file_table.c:348
task_work_run+0x1e1/0x250 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f49d399ce59
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:00007ffefddd27d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffefddd28c0 RCX: 00007f49d399ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000075e1 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b33120000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f49d3c15fac R14: 00007f49d3c15fa8 R15: 00007f49d3c15fa0
---[ end trace 0000000000000000 ]---