==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff88812fb2b800 by task syz.0.1377/4977
CPU: 0 PID: 4977 Comm: syz.0.1377 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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_ioctl+0xd1/0x960 net/l2tp/l2tp_ppp.c:1060
pppox_ioctl+0x1f6/0x330 drivers/net/ppp/pppox.c:93
sock_do_ioctl+0x114/0x330 net/socket.c:1192
sock_ioctl+0x475/0x700 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
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
RIP: 0033:0x7f88edd9e1eb
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f88eed49450 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000200000fe5000 RCX: 00007f88edd9e1eb
RDX: 00007f88eed49bd0 RSI: 000000004020ae46 RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000008
R10: 0000000000000004 R11: 0000000000000246 R12: 00000000fec00000
R13: 00007f88eed49bd0 R14: 0000200000fe8000 R15: 0000000000000003
Allocated by task 4977:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_alloc_info+0x1f/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+0xb4/0x1e0 mm/slab_common.c:951
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
l2tp_session_create+0x38/0xbd0 net/l2tp/l2tp_core.c:1614
pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771
__sys_connect_file net/socket.c:2001 [inline]
__sys_connect+0x3da/0x460 net/socket.c:2018
__do_sys_connect net/socket.c:2028 [inline]
__se_sys_connect net/socket.c:2025 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2025
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 4977:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x2b/0x40 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
pppol2tp_ioctl+0x748/0x960 net/l2tp/l2tp_ppp.c:-1
pppox_ioctl+0x1f6/0x330 drivers/net/ppp/pppox.c:93
sock_do_ioctl+0x114/0x330 net/socket.c:1192
sock_ioctl+0x475/0x700 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
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
The buggy address belongs to the object at ffff88812fb2b800
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
512-byte region [ffff88812fb2b800, ffff88812fb2ba00)
The buggy address belongs to the physical page:
page:ffffea0004beca00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12fb28
head:ffffea0004beca00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004bec700 dead000000000002 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 466, tgid 466 (syz-executor), ts 32488571893, free_ts 31809441036
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673
prep_new_page+0x1c/0x110 mm/page_alloc.c:2680
get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587
__alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931
alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
allocate_slab mm/slub.c:1967 [inline]
new_slab+0x98/0x3e0 mm/slub.c:2020
___slab_alloc+0x70f/0xb70 mm/slub.c:3177
__slab_alloc+0x5e/0xa0 mm/slub.c:3263
slab_alloc_node mm/slub.c:3348 [inline]
__kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423
__do_kmalloc_node mm/slab_common.c:937 [inline]
__kmalloc_node_track_caller+0xa1/0x1e0 mm/slab_common.c:958
kmalloc_reserve net/core/skbuff.c:449 [inline]
__alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
alloc_skb include/linux/skbuff.h:1322 [inline]
nlmsg_new include/net/netlink.h:987 [inline]
rtmsg_ifa+0xfa/0x1e0 net/ipv4/devinet.c:1933
__inet_insert_ifa+0x83f/0xa30 net/ipv4/devinet.c:567
inet_rtm_newaddr+0x8be/0x1650 net/ipv4/devinet.c:970
rtnetlink_rcv_msg+0xb28/0xde0 net/core/rtnetlink.c:6154
netlink_rcv_skb+0x200/0x450 net/netlink/af_netlink.c:2526
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1581 [inline]
free_pcp_prepare mm/page_alloc.c:1655 [inline]
free_unref_page_prepare+0x81b/0x820 mm/page_alloc.c:3622
free_unref_page+0x93/0x530 mm/page_alloc.c:3720
free_the_page mm/page_alloc.c:863 [inline]
__free_pages+0x67/0x100 mm/page_alloc.c:6021
__vunmap+0xa3c/0xc00 mm/vmalloc.c:2739
__vfree mm/vmalloc.c:2788 [inline]
vfree+0x61/0x90 mm/vmalloc.c:2819
kcov_put kernel/kcov.c:437 [inline]
kcov_close+0x2b/0x50 kernel/kcov.c:533
__fput+0x1fd/0x8f0 fs/file_table.c:320
____fput+0x15/0x20 fs/file_table.c:348
task_work_run+0x1e1/0x250 kernel/task_work.c:203
exit_task_work include/linux/task_work.h:39 [inline]
do_exit+0xb0d/0x29f0 kernel/exit.c:896
do_group_exit+0x21b/0x2e0 kernel/exit.c:1040
__do_sys_exit_group kernel/exit.c:1051 [inline]
__se_sys_exit_group kernel/exit.c:1049 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1049
x64_sys_call+0x7b4/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
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
Memory state around the buggy address:
ffff88812fb2b700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88812fb2b780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88812fb2b800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88812fb2b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88812fb2b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4977 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: 4977 Comm: syz.0.1377 Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 7c 2a d5 fc be 02 00 00 00 eb 0a e8 70 2a d5 fc be 01 00 00 00 4c 89 f7 e8 63 fb cc fd e9 0f ff ff ff e8 59 2a d5 fc <0f> 0b 48 89 df e8 ff 00 00 00 eb bd e8 48 2a d5 fc 4c 89 f7 be 03
RSP: 0018:ffffc900071efaf0 EFLAGS: 00010246
RAX: ffffffff849c43e7 RBX: ffff8881149b5000 RCX: 0000000000080000
RDX: ffffc900012c9000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc900071efb10 R08: ffffffff87b777e7 R09: 1ffffffff0f6eefc
R10: dffffc0000000000 R11: fffffbfff0f6eefd R12: dffffc0000000000
R13: ffffc900071efb60 R14: 000000003f1a3958 R15: ffff88812fb2b800
FS: 00007f88eed4b6c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c295a55 CR3: 0000000148c46000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
pppol2tp_ioctl+0xd1/0x960 net/l2tp/l2tp_ppp.c:1060
pppox_ioctl+0x1f6/0x330 drivers/net/ppp/pppox.c:93
sock_do_ioctl+0x114/0x330 net/socket.c:1192
sock_ioctl+0x475/0x700 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
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
RIP: 0033:0x7f88edd9e1eb
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f88eed49450 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000200000fe5000 RCX: 00007f88edd9e1eb
RDX: 00007f88eed49bd0 RSI: 000000004020ae46 RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000008
R10: 0000000000000004 R11: 0000000000000246 R12: 00000000fec00000
R13: 00007f88eed49bd0 R14: 0000200000fe8000 R15: 0000000000000003
---[ end trace 0000000000000000 ]---
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4977 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: 4977 Comm: syz.0.1377 Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 7c 2a d5 fc be 02 00 00 00 eb 0a e8 70 2a d5 fc be 01 00 00 00 4c 89 f7 e8 63 fb cc fd e9 0f ff ff ff e8 59 2a d5 fc <0f> 0b 48 89 df e8 ff 00 00 00 eb bd e8 48 2a d5 fc 4c 89 f7 be 03
RSP: 0018:ffffc900071efaf0 EFLAGS: 00010246
RAX: ffffffff849c43e7 RBX: ffff8881149b5000 RCX: 0000000000080000
RDX: ffffc900012c9000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc900071efb10 R08: ffff8881149b5083 R09: 1ffff11022936a10
R10: dffffc0000000000 R11: ffffed1022936a11 R12: dffffc0000000000
R13: ffffc900071efb60 R14: 000000003f1a3958 R15: ffff88812fb2b800
FS: 00007f88eed4b6c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc9c8b1118 CR3: 0000000148c46000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
pppol2tp_ioctl+0xd1/0x960 net/l2tp/l2tp_ppp.c:1060
pppox_ioctl+0x1f6/0x330 drivers/net/ppp/pppox.c:93
sock_do_ioctl+0x114/0x330 net/socket.c:1192
sock_ioctl+0x475/0x700 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
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
RIP: 0033:0x7f88edd9e1eb
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f88eed49450 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000200000fe5000 RCX: 00007f88edd9e1eb
RDX: 00007f88eed49bd0 RSI: 000000004020ae46 RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000008
R10: 0000000000000004 R11: 0000000000000246 R12: 00000000fec00000
R13: 00007f88eed49bd0 R14: 0000200000fe9000 R15: 0000000000000004
---[ end trace 0000000000000000 ]---
------------[ cut here ]------------
WARNING: CPU: 1 PID: 4977 at net/l2tp/l2tp_ppp.c:156 pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Modules linked in:
CPU: 1 PID: 4977 Comm: syz.0.1377 Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 7c 2a d5 fc be 02 00 00 00 eb 0a e8 70 2a d5 fc be 01 00 00 00 4c 89 f7 e8 63 fb cc fd e9 0f ff ff ff e8 59 2a d5 fc <0f> 0b 48 89 df e8 ff 00 00 00 eb bd e8 48 2a d5 fc 4c 89 f7 be 03
RSP: 0018:ffffc900071ef930 EFLAGS: 00010246
RAX: ffffffff849c43e7 RBX: ffff8881149b5000 RCX: 0000000000080000
RDX: ffffc900012c9000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc900071ef950 R08: ffff8881149b5083 R09: 1ffff11022936a10
R10: dffffc0000000000 R11: ffffed1022936a11 R12: dffffc0000000000
R13: dffffc0000000000 R14: 000000003f1a3958 R15: ffff88812fb2b800
FS: 00007f88eed4b6c0(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff7ab9f66b8 CR3: 0000000148c46000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:434
__sock_release net/socket.c:652 [inline]
sock_close+0xc9/0x220 net/socket.c:1390
__fput+0x1fd/0x8f0 fs/file_table.c:320
____fput+0x15/0x20 fs/file_table.c:348
task_work_run+0x1e1/0x250 kernel/task_work.c:203
get_signal+0x12e8/0x1700 kernel/signal.c:2677
arch_do_signal_or_restart+0xd1/0x11c0 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x7a/0xb0 kernel/entry/common.c:174
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: 0033:0x7f88edd9e1eb
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f88eed49450 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffe7 RBX: 0000200000fe5000 RCX: 00007f88edd9e1eb
RDX: 00007f88eed49bd0 RSI: 000000004020ae46 RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000008
R10: 0000000000000004 R11: 0000000000000246 R12: 00000000fec00000
R13: 00007f88eed49bd0 R14: 0000200000fe9000 R15: 0000000000000004
---[ end trace 0000000000000000 ]---