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================================================================== 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+0x24/0x4a0 net/l2tp/l2tp_core.c:1563 Write of size 8 at addr ffff8881180fe808 by task kworker/u4:3/296 CPU: 1 PID: 296 Comm: kworker/u4:3 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Workqueue: l2tp l2tp_tunnel_del_work Call Trace: __dump_stack+0x21/0x24 lib/dump_stack.c:77 dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:435 [inline] kasan_report+0xe2/0x130 mm/kasan/report.c:452 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x280/0x290 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+0x24/0x4a0 net/l2tp/l2tp_core.c:1563 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1218 [inline] l2tp_tunnel_del_work+0x1d2/0x3e0 net/l2tp/l2tp_core.c:1258 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447 kthread+0x346/0x3d0 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 Allocated by task 609: 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:430 [inline] ____kasan_kmalloc mm/kasan/common.c:509 [inline] __kasan_kmalloc+0xda/0x110 mm/kasan/common.c:518 kasan_kmalloc include/linux/kasan.h:254 [inline] __kmalloc+0x1a7/0x330 mm/slub.c:4038 kmalloc include/linux/slab.h:557 [inline] kzalloc include/linux/slab.h:664 [inline] l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1599 pppol2tp_connect+0xb35/0x1570 net/l2tp/l2tp_ppp.c:782 __sys_connect_file net/socket.c:1866 [inline] __sys_connect+0x38c/0x410 net/socket.c:1883 __do_sys_connect net/socket.c:1893 [inline] __se_sys_connect net/socket.c:1890 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1890 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb Freed by task 12: 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:362 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370 kasan_slab_free include/linux/kasan.h:220 [inline] slab_free_hook mm/slub.c:1600 [inline] slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626 slab_free mm/slub.c:3208 [inline] kfree+0xc0/0x270 mm/slub.c:4196 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_dec_refcount+0xb2/0x1a0 net/l2tp/l2tp_core.c:205 pppol2tp_session_destruct+0xb1/0xf0 net/l2tp/l2tp_ppp.c:419 __sk_destruct+0x53/0x600 net/core/sock.c:1818 sk_destruct net/core/sock.c:1863 [inline] __sk_free+0x313/0x410 net/core/sock.c:1874 sk_free+0x54/0x90 net/core/sock.c:1885 sock_put include/net/sock.h:1894 [inline] pppol2tp_put_sk+0x7a/0xb0 net/l2tp/l2tp_ppp.c:402 rcu_do_batch+0x4df/0xa80 kernel/rcu/tree.c:2494 rcu_core+0x55f/0xd60 kernel/rcu/tree.c:2735 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748 __do_softirq+0x255/0x563 kernel/softirq.c:309 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 kernel/rcu/tree.c:2980 [inline] call_rcu+0x10e/0x1050 kernel/rcu/tree.c:3054 pppol2tp_release+0x208/0x2d0 net/l2tp/l2tp_ppp.c:458 __sock_release net/socket.c:597 [inline] sock_close+0xe0/0x270 net/socket.c:1286 __fput+0x2fb/0x770 fs/file_table.c:281 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56 entry_SYSCALL_64_after_hwframe+0x61/0xcb The buggy address belongs to the object at ffff8881180fe800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 8 bytes inside of 512-byte region [ffff8881180fe800, ffff8881180fea00) The buggy address belongs to the page: page:ffffea0004603f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8881180ff400 pfn:0x1180fc head:ffffea0004603f00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea0004603e00 0000000200000002 ffff888100043080 raw: ffff8881180ff400 000000008010000d 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 108, ts 6174720410, free_ts 0 set_page_owner include/linux/page_owner.h:35 [inline] post_alloc_hook mm/page_alloc.c:2456 [inline] prep_new_page+0x179/0x180 mm/page_alloc.c:2462 get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5370 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1813 [inline] new_slab+0x84/0x3f0 mm/slub.c:1874 new_slab_objects mm/slub.c:2632 [inline] ___slab_alloc+0x2a6/0x450 mm/slub.c:2796 __slab_alloc+0x63/0xa0 mm/slub.c:2836 slab_alloc_node mm/slub.c:2918 [inline] slab_alloc mm/slub.c:2960 [inline] __kmalloc_track_caller+0x1ef/0x320 mm/slub.c:4541 __kmalloc_reserve net/core/skbuff.c:144 [inline] __alloc_skb+0xdc/0x520 net/core/skbuff.c:212 alloc_skb include/linux/skbuff.h:1126 [inline] alloc_skb_with_frags+0xa2/0x560 net/core/skbuff.c:5993 sock_alloc_send_pskb+0x853/0x980 net/core/sock.c:2393 unix_dgram_sendmsg+0x5f4/0x17d0 net/unix/af_unix.c:1725 sock_sendmsg_nosec net/socket.c:652 [inline] __sock_sendmsg net/socket.c:664 [inline] sock_write_iter+0x29c/0x380 net/socket.c:1018 call_write_iter include/linux/fs.h:2066 [inline] new_sync_write fs/read_write.c:518 [inline] vfs_write+0x725/0xd60 fs/read_write.c:605 ksys_write+0x140/0x240 fs/read_write.c:658 __do_sys_write fs/read_write.c:670 [inline] __se_sys_write fs/read_write.c:667 [inline] __x64_sys_write+0x7b/0x90 fs/read_write.c:667 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 page_owner free stack trace missing Memory state around the buggy address: ffff8881180fe700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881180fe780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8881180fe800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881180fe880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881180fe900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 296 at lib/refcount.c:28 refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28 Modules linked in: CPU: 0 PID: 296 Comm: kworker/u4:3 Tainted: G B syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Workqueue: l2tp l2tp_tunnel_del_work RIP: 0010:refcount_warn_saturate+0x120/0x1a0 lib/refcount.c:28 Code: 04 01 48 c7 c7 20 0e 20 85 e8 6c e5 34 02 0f 0b eb c3 e8 63 3b 29 ff c6 05 61 0a 66 04 01 48 c7 c7 80 0e 20 85 e8 50 e5 34 02 <0f> 0b eb a7 e8 47 3b 29 ff c6 05 42 0a 66 04 01 48 c7 c7 a0 0d 20 RSP: 0018:ffffc90007977c50 EFLAGS: 00010246 RAX: a8003238668fb000 RBX: 0000000000000003 RCX: ffff88812708a780 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: ffffc90007977c60 R08: 0000000000000004 R09: 0000000000000003 R10: fffff52000f2eed0 R11: 1ffff92000f2eed0 R12: ffff8881180ff820 R13: dffffc0000000000 R14: 0000000000000003 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c2a4c50 CR3: 0000000117b34000 CR4: 00000000003506b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __refcount_sub_and_test include/linux/refcount.h:283 [inline] __refcount_dec_and_test include/linux/refcount.h:315 [inline] refcount_dec_and_test include/linux/refcount.h:333 [inline] l2tp_session_dec_refcount+0xcb/0x1a0 net/l2tp/l2tp_core.c:204 l2tp_session_delete+0x3ab/0x4a0 net/l2tp/l2tp_core.c:1572 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1218 [inline] l2tp_tunnel_del_work+0x1d2/0x3e0 net/l2tp/l2tp_core.c:1258 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447 kthread+0x346/0x3d0 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 ---[ end trace 5078cb62afce4be7 ]---
| Time | Kernel | Commit | Syzkaller | Config | Log | Report | Syz repro | C repro | VM info | Assets (help?) | Manager | Title |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2025/10/28 07:03 | android13-5.10-lts | 2ece552169c2 | fd2207e7 | .config | console log | report | info | [disk image] [vmlinux] [kernel image] | ci2-android-5-10 | KASAN: use-after-free Write in l2tp_session_delete | ||
| 2025/09/15 04:30 | android13-5.10-lts | 911f602c2237 | e2beed91 | .config | console log | report | info | [disk image] [vmlinux] [kernel image] | ci2-android-5-10 | KASAN: use-after-free Write in l2tp_session_delete |