F2FS-fs (loop8): Mounted with checkpoint version = 48b305e5
==================================================================
BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
Read of size 4 at addr ffff88811ae49800 by task syz.8.1314/4889

CPU: 0 PID: 4889 Comm: syz.8.1314 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __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_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156
 pppol2tp_sendmsg+0xdf/0x5f0 net/l2tp/l2tp_ppp.c:271
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2435
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2489
 __sys_sendmmsg+0x2ba/0x4e0 net/socket.c:2575
 __do_sys_sendmmsg net/socket.c:2604 [inline]
 __se_sys_sendmmsg net/socket.c:2601 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2601
 x64_sys_call+0x6c6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:308
 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: 0033:0x7f79ffec1e59
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:00007f79fe91c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f7a0013afa0 RCX: 00007f79ffec1e59
RDX: 04000000000001ce RSI: 0000200000005f80 RDI: 0000000000000004
RBP: 00007f79fff57e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000008040 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a0013b038 R14: 00007f7a0013afa0 R15: 00007ffff086ead8
 </TASK>

Allocated by task 4889:
 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 4889:
 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
 pppol2tp_ioctl+0x748/0x960 net/l2tp/l2tp_ppp.c:-1
 pppox_ioctl+0x1e4/0x320 drivers/net/ppp/pppox.c:93
 sock_do_ioctl+0x103/0x310 net/socket.c:1137
 sock_ioctl+0x459/0x6d0 net/socket.c:1256
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:860
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:860
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 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

The buggy address belongs to the object at ffff88811ae49800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff88811ae49800, ffff88811ae49a00)
The buggy address belongs to the page:
page:ffffea00046b9200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11ae48
head:ffffea00046b9200 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 0000000600000001 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 139, ts 7174575995, free_ts 6912772627
 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:6207
 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2542
 unix_dgram_sendmsg+0x6f3/0x19b0 net/unix/af_unix.c:1816
 unix_seqpacket_sendmsg+0x118/0x1e0 net/unix/af_unix.c:2277
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 sock_write_iter+0x2a6/0x3a0 net/socket.c:1079
 do_iter_readv_writev+0x477/0x5f0 fs/read_write.c:-1
 do_iter_write+0x207/0x7b0 fs/read_write.c:855
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_pages_ok+0xa13/0xae0 mm/page_alloc.c:1774
 free_the_page mm/page_alloc.c:807 [inline]
 __free_pages+0xf6/0x100 mm/page_alloc.c:5900
 free_nonslab_page+0x86/0xc0 mm/slub.c:3564
 kfree+0x19a/0x270 mm/slub.c:4585
 kvfree+0x35/0x40 mm/util.c:661
 proc_sys_call_handler+0x581/0x7c0 fs/proc/proc_sysctl.c:602
 proc_sys_read+0x1f/0x30 fs/proc/proc_sysctl.c:611
 call_read_iter include/linux/fs.h:2206 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x6c0/0xc20 fs/read_write.c:485
 ksys_read+0x14a/0x260 fs/read_write.c:623
 __do_sys_read fs/read_write.c:633 [inline]
 __se_sys_read fs/read_write.c:631 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:631
 x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 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

Memory state around the buggy address:
 ffff88811ae49700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88811ae49780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88811ae49800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88811ae49880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811ae49900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4889 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: 4889 Comm: syz.8.1314 Tainted: G    B   W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 cc f2 0b fd be 02 00 00 00 eb 0a e8 c0 f2 0b fd be 01 00 00 00 4c 89 f7 e8 13 62 f2 fd e9 0f ff ff ff e8 a9 f2 0b fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 98 f2 0b fd 4c 89 f7 be 03
RSP: 0018:ffffc90000dff898 EFLAGS: 00010246
RAX: ffffffff845db907 RBX: ffff888126ab6000 RCX: 0000000000080000
RDX: ffffc90002a37000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc90000dff8b8 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e18c4c R12: dffffc0000000000
R13: 0000000000000001 R14: 000000001ae796f0 R15: ffff88811ae49800
FS:  00007f79fe91c6c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd6cae0d90 CR3: 000000010d7cb000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 pppol2tp_sendmsg+0xdf/0x5f0 net/l2tp/l2tp_ppp.c:271
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2435
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2489
 __sys_sendmmsg+0x2ba/0x4e0 net/socket.c:2575
 __do_sys_sendmmsg net/socket.c:2604 [inline]
 __se_sys_sendmmsg net/socket.c:2601 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2601
 x64_sys_call+0x6c6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:308
 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: 0033:0x7f79ffec1e59
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:00007f79fe91c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f7a0013afa0 RCX: 00007f79ffec1e59
RDX: 04000000000001ce RSI: 0000200000005f80 RDI: 0000000000000004
RBP: 00007f79fff57e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000008040 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a0013b038 R14: 00007f7a0013afa0 R15: 00007ffff086ead8
 </TASK>
---[ end trace 9cf1a25569e01a32 ]---
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4889 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: 4889 Comm: syz.8.1314 Tainted: G    B   W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156
Code: 5d c3 e8 cc f2 0b fd be 02 00 00 00 eb 0a e8 c0 f2 0b fd be 01 00 00 00 4c 89 f7 e8 13 62 f2 fd e9 0f ff ff ff e8 a9 f2 0b fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 98 f2 0b fd 4c 89 f7 be 03
RSP: 0018:ffffc90000dffa48 EFLAGS: 00010246
RAX: ffffffff845db907 RBX: ffff888126ab6000 RCX: 0000000000080000
RDX: ffffc90002a37000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc90000dffa68 R08: ffff888126ab6083 R09: 1ffff11024d56c10
R10: dffffc0000000000 R11: ffffed1024d56c11 R12: dffffc0000000000
R13: dffffc0000000000 R14: 000000001ae796f0 R15: ffff88811ae49800
FS:  00007f79fe91c6c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd6cae0d90 CR3: 000000010d7cb000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:435
 __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
 get_signal+0x13b1/0x1430 kernel/signal.c:2679
 arch_do_signal_or_restart+0xe2/0x1100 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
 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
RIP: 0033:0x7f79ffec1e59
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:00007f79fe91c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: fffffffffffffff7 RBX: 00007f7a0013afa0 RCX: 00007f79ffec1e59
RDX: 04000000000001ce RSI: 0000200000005f80 RDI: 0000000000000004
RBP: 00007f79fff57e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000008040 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a0013b038 R14: 00007f7a0013afa0 R15: 00007ffff086ead8
 </TASK>
---[ end trace 9cf1a25569e01a33 ]---