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================================================================== BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:102 [inline] BUG: KASAN: use-after-free in test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline] BUG: KASAN: use-after-free in l2tp_session_delete+0x27/0x4e0 net/l2tp/l2tp_core.c:1561 Write of size 8 at addr ffff88812986f008 by task kworker/u4:4/348 CPU: 0 PID: 348 Comm: kworker/u4:4 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Workqueue: l2tp l2tp_tunnel_del_work Call Trace: <TASK> __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 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37 instrument_atomic_read_write include/linux/instrumented.h:102 [inline] test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline] l2tp_session_delete+0x27/0x4e0 net/l2tp/l2tp_core.c:1561 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1216 [inline] l2tp_tunnel_del_work+0x201/0x420 net/l2tp/l2tp_core.c:1256 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 </TASK> Allocated by task 3168: 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:1597 pppol2tp_connect+0xb91/0x15b0 net/l2tp/l2tp_ppp.c:781 __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 13: 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_dec_refcount+0xaf/0x1a0 net/l2tp/l2tp_core.c:205 pppol2tp_session_destruct+0xb1/0xf0 net/l2tp/l2tp_ppp.c:418 __sk_destruct+0x64/0x600 net/core/sock.c:2153 sk_destruct net/core/sock.c:2198 [inline] __sk_free+0x313/0x410 net/core/sock.c:2209 sk_free+0x54/0x90 net/core/sock.c:2220 sock_put include/net/sock.h:2098 [inline] pppol2tp_put_sk+0x7a/0xb0 net/l2tp/l2tp_ppp.c:401 rcu_do_batch+0x52a/0xbc0 kernel/rcu/tree.c:2297 rcu_core+0x5c3/0xe80 kernel/rcu/tree.c:2557 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2574 handle_softirqs+0x1d7/0x600 kernel/softirq.c:642 run_ksoftirqd+0x28/0x30 kernel/softirq.c:1019 smpboot_thread_fn+0x4a0/0x910 kernel/smpboot.c:164 kthread+0x281/0x320 kernel/kthread.c:386 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46 __kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496 __call_rcu_common kernel/rcu/tree.c:2807 [inline] call_rcu+0xcf/0xf90 kernel/rcu/tree.c:2926 pppol2tp_release+0x208/0x2d0 net/l2tp/l2tp_ppp.c:457 __sock_release net/socket.c:652 [inline] sock_close+0xf1/0x290 net/socket.c:1390 __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 The buggy address belongs to the object at ffff88812986f000 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 8 bytes inside of 512-byte region [ffff88812986f000, ffff88812986f200) The buggy address belongs to the physical page: page:ffffea0004a61b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12986c head:ffffea0004a61b00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 ffffea0004a61a00 dead000000000003 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 2543, tgid 2543 (syz-executor), ts 91218474548, free_ts 90531195419 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2643 prep_new_page+0x1c/0x110 mm/page_alloc.c:2650 get_page_from_freelist+0x2d12/0x2d80 mm/page_alloc.c:4554 __alloc_pages+0x1d9/0x480 mm/page_alloc.c:5868 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 kmalloc_trace+0x29/0xb0 mm/slab_common.c:1028 kmalloc include/linux/slab.h:563 [inline] kzalloc include/linux/slab.h:699 [inline] ipv6_add_addr+0x411/0xe80 net/ipv6/addrconf.c:1119 addrconf_add_linklocal+0x20e/0x660 net/ipv6/addrconf.c:3283 addrconf_addr_gen+0x542/0x690 net/ipv6/addrconf.c:3414 addrconf_init_auto_addrs+0x841/0xb80 net/ipv6/addrconf.c:-1 addrconf_notify+0x803/0xe40 net/ipv6/addrconf.c:3711 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1551 [inline] free_pcp_prepare mm/page_alloc.c:1625 [inline] free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3589 free_unref_page+0x95/0x540 mm/page_alloc.c:3687 free_the_page mm/page_alloc.c:836 [inline] __free_pages+0x67/0x100 mm/page_alloc.c:5957 __vunmap+0x9c0/0xb80 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+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 exit_task_work include/linux/task_work.h:39 [inline] do_exit+0xa35/0x2660 kernel/exit.c:886 do_group_exit+0x210/0x2d0 kernel/exit.c:1028 __do_sys_exit_group kernel/exit.c:1039 [inline] __se_sys_exit_group kernel/exit.c:1037 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1037 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: ffff88812986ef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88812986ef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88812986f000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88812986f080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88812986f100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
| Time | Kernel | Commit | Syzkaller | Config | Log | Report | Syz repro | C repro | VM info | Assets (help?) | Manager | Title |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026/02/21 02:03 | android14-6.1 | edbe3e111301 | 6e7b5511 | .config | console log | report | info | [disk image] [vmlinux] [kernel image] | ci2-android-6-1 | KASAN: use-after-free Write in l2tp_session_delete |