================================================================== BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:102 [inline] BUG: KASAN: use-after-free in atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:1779 [inline] BUG: KASAN: use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:176 [inline] BUG: KASAN: use-after-free in mutex_lock+0x86/0x1b0 kernel/locking/mutex.c:295 Write of size 8 at addr ffff888131d69550 by task syz.1.5117/15405 CPU: 1 PID: 15405 Comm: syz.1.5117 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Call Trace: __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] atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:1779 [inline] __mutex_trylock_fast kernel/locking/mutex.c:176 [inline] mutex_lock+0x86/0x1b0 kernel/locking/mutex.c:295 pppol2tp_release+0x178/0x2b0 net/l2tp/l2tp_ppp.c:441 __sock_release net/socket.c:652 [inline] sock_close+0xc9/0x220 net/socket.c:1389 __fput+0x1fd/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 RIP: 0033:0x7f678d79ce59 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:00007fffa9da83a8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007f678da17da0 RCX: 00007f678d79ce59 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007f678da17da0 R08: 0000000000000006 R09: 0000000000000000 R10: 00007f678da17cb0 R11: 0000000000000246 R12: 00000000000e2b50 R13: 00007f678da1609c R14: 00000000000e2891 R15: 00007f678da16090 Allocated by task 15408: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_alloc_info+0x1f/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+0xb4/0x1e0 mm/slab_common.c:951 kmalloc include/linux/slab.h:568 [inline] kzalloc include/linux/slab.h:699 [inline] l2tp_session_create+0x38/0xbd0 net/l2tp/l2tp_core.c:1609 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771 __sys_connect_file net/socket.c:2000 [inline] __sys_connect+0x3da/0x460 net/socket.c:2017 __do_sys_connect net/socket.c:2027 [inline] __se_sys_connect net/socket.c:2024 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2024 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 15405: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_free_info+0x2b/0x40 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_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193 l2tp_session_delete+0x3df/0x4d0 net/l2tp/l2tp_core.c:1582 pppol2tp_release+0x169/0x2b0 net/l2tp/l2tp_ppp.c:438 __sock_release net/socket.c:652 [inline] sock_close+0xc9/0x220 net/socket.c:1389 __fput+0x1fd/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 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 kvfree_call_rcu+0x8b/0x7a0 kernel/rcu/tree.c:3445 inet6_ifa_finish_destroy+0x129/0x1b0 net/ipv6/addrconf.c:1007 in6_ifa_put include/net/addrconf.h:459 [inline] addrconf_ifdown+0x1254/0x1950 net/ipv6/addrconf.c:3960 addrconf_notify+0x39f/0xe30 net/ipv6/addrconf.c:-1 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455 call_netdevice_notifiers_info net/core/dev.c:2022 [inline] call_netdevice_notifiers_extack net/core/dev.c:2060 [inline] call_netdevice_notifiers net/core/dev.c:2074 [inline] __dev_notify_flags+0x276/0x5b0 net/core/dev.c:8732 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8768 do_setlink+0xc02/0x2a10 net/core/rtnetlink.c:2836 rtnl_group_changelink net/core/rtnetlink.c:3364 [inline] __rtnl_newlink net/core/rtnetlink.c:3621 [inline] rtnl_newlink+0x10b3/0x20d0 net/core/rtnetlink.c:3658 rtnetlink_rcv_msg+0xb28/0xde0 net/core/rtnetlink.c:6153 netlink_rcv_skb+0x200/0x450 net/netlink/af_netlink.c:2521 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6171 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x8c1/0xa60 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x8b9/0xbd0 net/netlink/af_netlink.c:1873 sock_sendmsg_nosec net/socket.c:716 [inline] __sock_sendmsg net/socket.c:728 [inline] ____sys_sendmsg+0x5fb/0x9c0 net/socket.c:2508 ___sys_sendmsg+0x2a2/0x360 net/socket.c:2562 __sys_sendmsg net/socket.c:2591 [inline] __do_sys_sendmsg net/socket.c:2600 [inline] __se_sys_sendmsg net/socket.c:2598 [inline] __x64_sys_sendmsg+0x20d/0x2e0 net/socket.c:2598 x64_sys_call+0x171/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:47 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 Second to 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 insert_work+0x51/0x300 kernel/workqueue.c:1368 __queue_work+0x9d0/0xd50 kernel/workqueue.c:1527 __queue_delayed_work+0x188/0x200 kernel/workqueue.c:1675 mod_delayed_work_on+0x74/0xe0 kernel/workqueue.c:1749 mod_delayed_work include/linux/workqueue.h:540 [inline] addrconf_mod_dad_work+0x7d/0x120 net/ipv6/addrconf.c:335 addrconf_dad_start+0x96/0xd0 net/ipv6/addrconf.c:4139 inet6_addr_add+0x650/0x9c0 net/ipv6/addrconf.c:3057 inet6_rtm_newaddr+0x74a/0xa10 net/ipv6/addrconf.c:4999 rtnetlink_rcv_msg+0xb28/0xde0 net/core/rtnetlink.c:6153 netlink_rcv_skb+0x200/0x450 net/netlink/af_netlink.c:2521 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6171 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x8c1/0xa60 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x8b9/0xbd0 net/netlink/af_netlink.c:1873 sock_sendmsg_nosec net/socket.c:716 [inline] __sock_sendmsg net/socket.c:728 [inline] __sys_sendto+0x4ac/0x660 net/socket.c:2142 __do_sys_sendto net/socket.c:2154 [inline] __se_sys_sendto net/socket.c:2150 [inline] __x64_sys_sendto+0xe5/0x100 net/socket.c:2150 x64_sys_call+0x83/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45 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 The buggy address belongs to the object at ffff888131d69400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 336 bytes inside of 512-byte region [ffff888131d69400, ffff888131d69600) The buggy address belongs to the physical page: page:ffffea0004c75a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x131d68 head:ffffea0004c75a00 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 287, tgid 287 (syz-executor), ts 33227989071, free_ts 0 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672 prep_new_page+0x1c/0x110 mm/page_alloc.c:2679 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4586 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5930 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1 allocate_slab mm/slub.c:1967 [inline] new_slab+0x98/0x3e0 mm/slub.c:2020 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177 __slab_alloc+0x5e/0xa0 mm/slub.c:3263 slab_alloc_node mm/slub.c:3348 [inline] __kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423 __do_kmalloc_node mm/slab_common.c:937 [inline] __kmalloc+0xa4/0x1e0 mm/slab_common.c:951 kmalloc include/linux/slab.h:568 [inline] kzalloc include/linux/slab.h:699 [inline] fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:156 ip6_route_info_create+0x51b/0x14d0 net/ipv6/route.c:3796 ip6_route_add+0x27/0x130 net/ipv6/route.c:3892 addrconf_prefix_route+0x233/0x310 net/ipv6/addrconf.c:2466 inet6_addr_add+0x527/0x9c0 net/ipv6/addrconf.c:3042 inet6_rtm_newaddr+0x74a/0xa10 net/ipv6/addrconf.c:4999 page_owner free stack trace missing Memory state around the buggy address: ffff888131d69400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888131d69480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888131d69500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888131d69580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888131d69600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================