[Android 5.15] KASAN: use-after-free Write in l2tp_session_delete (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7d1f9b5c2ff5 Merge branch 'android13-5.15' into android13-..
git tree: android13-5.15-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=12353654580000
kernel config: https://syzkaller.appspot.com/x/.config?x=965f2bb6f70e8842
dashboard link: https://syzkaller.appspot.com/bug?extid=24be2e83007366ad36f9
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=103a9874580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17a3e060580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/36970cc43bac/disk-7d1f9b5c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5316820505f2/vmlinux-7d1f9b5c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/96af69e20c57/bzImage-7d1f9b5c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+24be2e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:70 [inline]
BUG: KASAN: use-after-free in l2tp_session_delete+0x24/0x4e0 net/l2tp/l2tp_core.c:1563
Write of size 8 at addr ffff8881166a7408 by task kworker/u4:3/353

CPU: 1 PID: 353 Comm: kworker/u4:3 Not tainted 5.15.178-syzkaller-00013-g7d1f9b5c2ff5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x151/0x1c0 lib/dump_stack.c:106
print_address_description+0x87/0x3b0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:427 [inline]
kasan_report+0x179/0x1c0 mm/kasan/report.c:444
kasan_check_range+0x293/0x2a0 mm/kasan/generic.c:189
__kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:70 [inline]
l2tp_session_delete+0x24/0x4e0 net/l2tp/l2tp_core.c:1563
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1218 [inline]
l2tp_tunnel_del_work+0x19d/0x380 net/l2tp/l2tp_core.c:1258
process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
kthread+0x421/0x510 kernel/kthread.c:337
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>

Allocated by task 649:
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+0xdb/0x110 mm/kasan/common.c:512
__kasan_kmalloc+0x9/0x10 mm/kasan/common.c:521
kasan_kmalloc include/linux/kasan.h:227 [inline]
__kmalloc+0x13f/0x2c0 mm/slub.c:4431
kmalloc include/linux/slab.h:608 [inline]
kzalloc include/linux/slab.h:733 [inline]
l2tp_session_create+0x38/0xb60 net/l2tp/l2tp_core.c:1599
pppol2tp_connect+0xc5d/0x1690 net/l2tp/l2tp_ppp.c:782
__sys_connect_file net/socket.c:1923 [inline]
__sys_connect+0x38b/0x410 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+0x14e/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 333:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0x126/0x160 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:1723 [inline]
slab_free_freelist_hook+0xbd/0x190 mm/slub.c:1749
slab_free mm/slub.c:3521 [inline]
kfree+0xcc/0x270 mm/slub.c:4583
l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
l2tp_session_dec_refcount+0xa9/0x1b0 net/l2tp/l2tp_core.c:205
pppol2tp_session_destruct+0xaf/0xf0 net/l2tp/l2tp_ppp.c:419
__sk_destruct+0x56/0x5b0 net/core/sock.c:1964
sk_destruct net/core/sock.c:2009 [inline]
__sk_free+0x36c/0x470 net/core/sock.c:2020
sk_free+0x51/0x80 net/core/sock.c:2031
sock_put include/net/sock.h:1929 [inline]
pppol2tp_put_sk+0x77/0xb0 net/l2tp/l2tp_ppp.c:402
rcu_do_batch+0x57a/0xc10 kernel/rcu/tree.c:2523
rcu_core+0x517/0x1020 kernel/rcu/tree.c:2763
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
handle_softirqs+0x25e/0x5c0 kernel/softirq.c:565
__do_softirq+0xb/0xd kernel/softirq.c:603

Last potentially related work creation:
kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xd3/0xf0 mm/kasan/generic.c:348
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
__call_rcu_common kernel/rcu/tree.c:3007 [inline]
call_rcu+0x123/0x10b0 kernel/rcu/tree.c:3125
pppol2tp_release+0x20f/0x2d0 net/l2tp/l2tp_ppp.c:458
__sock_release net/socket.c:649 [inline]
sock_close+0xdf/0x270 net/socket.c:1336
__fput+0x228/0x8c0 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:308
task_work_run+0x129/0x190 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0xc4/0xe0 kernel/entry/common.c:181
exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x26/0x160 kernel/entry/common.c:307
do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Second to last potentially related work creation:
kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xd3/0xf0 mm/kasan/generic.c:348
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
__call_rcu_common kernel/rcu/tree.c:3007 [inline]
call_rcu+0x123/0x10b0 kernel/rcu/tree.c:3125
pppol2tp_release+0x20f/0x2d0 net/l2tp/l2tp_ppp.c:458
__sock_release net/socket.c:649 [inline]
sock_close+0xdf/0x270 net/socket.c:1336
__fput+0x228/0x8c0 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:308
task_work_run+0x129/0x190 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0xc4/0xe0 kernel/entry/common.c:181
exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x26/0x160 kernel/entry/common.c:307
do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff8881166a7400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 8 bytes inside of
512-byte region [ffff8881166a7400, ffff8881166a7600)
The buggy address belongs to the page:
page:ffffea000459a900 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1166a4
head:ffffea000459a900 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea000459c500 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 114, ts 7683269238, free_ts 0
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
__alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5780
allocate_slab mm/slub.c:1932 [inline]
new_slab+0x9a/0x4e0 mm/slub.c:1995
___slab_alloc+0x39e/0x830 mm/slub.c:3028
__slab_alloc+0x4a/0x90 mm/slub.c:3115
slab_alloc_node mm/slub.c:3206 [inline]
slab_alloc mm/slub.c:3250 [inline]
__kmalloc_track_caller+0x171/0x2c0 mm/slub.c:4949
kmalloc_reserve net/core/skbuff.c:357 [inline]
__alloc_skb+0x10c/0x550 net/core/skbuff.c:428
alloc_skb include/linux/skbuff.h:1183 [inline]
alloc_skb_with_frags+0xa6/0x680 net/core/skbuff.c:6194
sock_alloc_send_pskb+0x915/0xa50 net/core/sock.c:2539
unix_dgram_sendmsg+0x6fd/0x2090 net/unix/af_unix.c:1805
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
sock_write_iter+0x39b/0x530 net/socket.c:1079
call_write_iter include/linux/fs.h:2206 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0xd5d/0x1110 fs/read_write.c:594
ksys_write+0x199/0x2c0 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:
ffff8881166a7300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881166a7380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881166a7400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881166a7480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881166a7500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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