================================================================== 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 ffff888121a59808 by task kworker/u4:3/310 CPU: 0 PID: 310 Comm: kworker/u4:3 Not tainted 5.15.185-syzkaller-00032-g0d918fa8e88d #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: l2tp l2tp_tunnel_del_work Call Trace: __dump_stack+0x21/0x30 lib/dump_stack.c:88 dump_stack_lvl+0xee/0x150 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+0xf1/0x140 mm/kasan/report.c:444 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+0x6be/0xba0 kernel/workqueue.c:2325 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472 kthread+0x411/0x500 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 Allocated by task 4388: 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+0xda/0x110 mm/kasan/common.c:521 kasan_kmalloc include/linux/kasan.h:227 [inline] __kmalloc+0x13d/0x2c0 mm/slub.c:4431 kmalloc include/linux/slab.h:621 [inline] kzalloc include/linux/slab.h:747 [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:1923 [inline] __sys_connect+0x389/0x410 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+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 4381: 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:1723 [inline] slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1749 slab_free mm/slub.c:3521 [inline] kfree+0xc4/0x270 mm/slub.c:4583 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:419 __sk_destruct+0x56/0x5e0 net/core/sock.c:1962 sk_destruct net/core/sock.c:2007 [inline] __sk_free+0x313/0x410 net/core/sock.c:2018 sk_free+0x54/0x90 net/core/sock.c:2029 sock_put include/net/sock.h:1939 [inline] pppol2tp_put_sk+0x7a/0xb0 net/l2tp/l2tp_ppp.c:402 rcu_do_batch+0x51d/0xba0 kernel/rcu/tree.c:2523 rcu_core+0x5e4/0xf80 kernel/rcu/tree.c:2763 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776 handle_softirqs+0x250/0x560 kernel/softirq.c:583 __do_softirq kernel/softirq.c:621 [inline] invoke_softirq kernel/softirq.c:443 [inline] __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670 irq_exit_rcu+0x9/0x10 kernel/softirq.c:682 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline] sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1108 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:676 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_common kernel/rcu/tree.c:3007 [inline] call_rcu+0xf6/0xf60 kernel/rcu/tree.c:3125 pppol2tp_release+0x208/0x2d0 net/l2tp/l2tp_ppp.c:458 __sock_release net/socket.c:649 [inline] sock_close+0xe0/0x270 net/socket.c:1336 __fput+0x20b/0x8b0 fs/file_table.c:311 ____fput+0x15/0x20 fs/file_table.c:339 task_work_run+0x127/0x190 kernel/task_work.c:188 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop+0xd0/0xe0 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+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 The buggy address belongs to the object at ffff888121a59800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 8 bytes inside of 512-byte region [ffff888121a59800, ffff888121a59a00) The buggy address belongs to the page: page:ffffea0004869600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121a58 head:ffffea0004869600 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 dead000000000100 dead000000000122 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 435, ts 40366588682, free_ts 38682266427 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611 get_page_from_freelist+0x2cc5/0x2d50 mm/page_alloc.c:4485 __alloc_pages+0x18f/0x440 mm/page_alloc.c:5795 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1932 [inline] new_slab+0xa1/0x4d0 mm/slub.c:1995 ___slab_alloc+0x381/0x810 mm/slub.c:3028 __slab_alloc+0x49/0x90 mm/slub.c:3115 slab_alloc_node mm/slub.c:3206 [inline] slab_alloc mm/slub.c:3250 [inline] __kmalloc+0x16a/0x2c0 mm/slub.c:4427 kmalloc include/linux/slab.h:621 [inline] kzalloc include/linux/slab.h:747 [inline] fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:155 ip6_route_info_create+0x526/0x1510 net/ipv6/route.c:3784 addrconf_f6i_alloc+0x154/0x360 net/ipv6/route.c:4584 ipv6_add_addr+0x40b/0xd40 net/ipv6/addrconf.c:1123 addrconf_add_linklocal+0x21b/0x620 net/ipv6/addrconf.c:3259 addrconf_addr_gen+0x48b/0x5b0 net/ipv6/addrconf.c:3390 addrconf_dev_config net/ipv6/addrconf.c:3435 [inline] addrconf_init_auto_addrs+0x8c4/0xcd0 net/ipv6/addrconf.c:3519 addrconf_notify+0x95d/0xde0 net/ipv6/addrconf.c:3688 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1472 [inline] free_pcp_prepare mm/page_alloc.c:1544 [inline] free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534 free_unref_page+0xa2/0x550 mm/page_alloc.c:3616 free_the_page mm/page_alloc.c:805 [inline] __free_pages+0x6c/0x100 mm/page_alloc.c:5871 __vunmap+0x84d/0x9e0 mm/vmalloc.c:2652 __vfree mm/vmalloc.c:2701 [inline] vfree+0x8b/0xc0 mm/vmalloc.c:2732 kcov_put kernel/kcov.c:417 [inline] kcov_close+0x2b/0x50 kernel/kcov.c:519 __fput+0x20b/0x8b0 fs/file_table.c:311 ____fput+0x15/0x20 fs/file_table.c:339 task_work_run+0x127/0x190 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xa76/0x27a0 kernel/exit.c:880 do_group_exit+0x141/0x310 kernel/exit.c:1002 __do_sys_exit_group kernel/exit.c:1013 [inline] __se_sys_exit_group kernel/exit.c:1011 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1011 x64_sys_call+0x832/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232 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: ffff888121a59700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888121a59780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888121a59800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888121a59880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888121a59900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================