KASAN: use-after-free Write in rcu_segcblist_enqueue

Status: upstream: reported C repro on 2026/06/14 23:49
Reported-by: syzbot+f3d0e223825d6eb4786d@syzkaller.appspotmail.com
First crash: 54d, last: 3h13m
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue 22 syz, C 101 5h05m 42d 0/2 upstream: reported C repro on 2026/06/22 22:11
android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue origin:upstream 22 syz, C 34 11h38m 36d 0/2 upstream: reported C repro on 2026/06/29 08:43
upstream general protection fault in rcu_segcblist_enqueue kvm-x86 2 syz, C done done 368 1793d 1857d 20/29 fixed on 2022/03/08 16:11

Sample crash report:
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
==================================================================
BUG: KASAN: use-after-free in rcu_segcblist_enqueue+0x9c/0xb0 kernel/rcu/rcu_segcblist.c:346
Write of size 8 at addr ffff888113e08590 by task kworker/u4:2/43

CPU: 0 PID: 43 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report_generic.c:356
 rcu_segcblist_enqueue+0x9c/0xb0 kernel/rcu/rcu_segcblist.c:346
 __call_rcu_common kernel/rcu/tree.c:2827 [inline]
 call_rcu+0x554/0xf50 kernel/rcu/tree.c:2926
 radix_tree_node_free lib/radix-tree.c:308 [inline]
 delete_node+0x1c0/0xa60 lib/radix-tree.c:571
 __radix_tree_delete+0x2c3/0x3a0 lib/radix-tree.c:1377
 radix_tree_delete_item+0x2fc/0x410 lib/radix-tree.c:1428
 idr_remove+0x43/0x60 lib/idr.c:156
 l2tp_tunnel_remove net/l2tp/l2tp_core.c:1256 [inline]
 l2tp_tunnel_del_work+0x385/0x410 net/l2tp/l2tp_core.c:1280
 process_one_work+0x717/0xc30 kernel/workqueue.c:2302
 worker_thread+0xa4d/0x11d0 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 376:
 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 43:
 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
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1228 [inline]
 l2tp_tunnel_del_work+0x199/0x410 net/l2tp/l2tp_core.c:1266
 process_one_work+0x717/0xc30 kernel/workqueue.c:2302
 worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449
 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/0xf50 kernel/rcu/tree.c:2926
 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:446
 __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

The buggy address belongs to the object at ffff888113e08400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff888113e08400, ffff888113e08600)

The buggy address belongs to the physical page:
page:ffffea00044f8200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x113e08
head:ffffea00044f8200 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000122 ffff888100042f00
raw: 0000000000000000 0000000080100010 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 0x152a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 371, tgid 371 (syz-executor), ts 27263270310, free_ts 26674128501
 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 net/ipv6/addrconf.c:2466 [inline]
 fixup_permanent_addr net/ipv6/addrconf.c:3569 [inline]
 addrconf_permanent_addr+0x635/0x940 net/ipv6/addrconf.c:3593
 addrconf_notify+0x7ca/0xe30 net/ipv6/addrconf.c:3665
 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:1580 [inline]
 free_pcp_prepare mm/page_alloc.c:1654 [inline]
 free_unref_page_prepare+0x80c/0x820 mm/page_alloc.c:3621
 free_unref_page+0x93/0x530 mm/page_alloc.c:3719
 free_the_page mm/page_alloc.c:863 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:6020
 __vunmap+0xa3c/0xc00 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+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
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0xaf2/0x2850 kernel/exit.c:887
 do_group_exit+0x21b/0x2e0 kernel/exit.c:1030
 get_signal+0x167c/0x1700 kernel/signal.c:2895
 arch_do_signal_or_restart+0xd1/0x11c0 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x7a/0xb0 kernel/entry/common.c:174
 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

Memory state around the buggy address:
 ffff888113e08480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888113e08500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888113e08580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888113e08600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888113e08680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (156):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/04 01:49 android14-6.1 92668decd5e0 9451e17e .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/03 12:59 android14-6.1 92668decd5e0 6b7c9f71 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/28 18:58 android14-6.1 83f1262811ad fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/14 23:37 android14-6.1 f17c14b8ada7 1d2f3589 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/03 20:34 android14-6.1 92668decd5e0 6b7c9f71 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/04 14:36 android14-6.1 92668decd5e0 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/03 23:32 android14-6.1 92668decd5e0 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/03 09:33 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/03 04:08 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/02 23:40 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/02 12:34 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/02 09:07 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/01 22:38 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/01 21:24 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/01 14:22 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/01 03:06 android14-6.1 92668decd5e0 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/31 05:40 android14-6.1 92668decd5e0 aaffb173 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/30 18:49 android14-6.1 92668decd5e0 aaffb173 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/30 07:37 android14-6.1 92668decd5e0 2377cd3d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/30 06:27 android14-6.1 92668decd5e0 6ef5c1e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/29 17:45 android14-6.1 92668decd5e0 6ef5c1e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/29 15:35 android14-6.1 92668decd5e0 6ef5c1e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/29 04:34 android14-6.1 92668decd5e0 19622d9d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/29 02:05 android14-6.1 92668decd5e0 19622d9d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/28 14:15 android14-6.1 92668decd5e0 edc8a875 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/27 11:57 android14-6.1 92668decd5e0 aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/27 11:54 android14-6.1 92668decd5e0 aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/27 10:50 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/27 05:20 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/27 01:29 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/26 16:03 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/26 11:01 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/26 07:40 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/26 00:25 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 22:35 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 17:17 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 15:59 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 12:41 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 02:02 android14-6.1 92668decd5e0 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/24 19:52 android14-6.1 92668decd5e0 dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/24 14:41 android14-6.1 92668decd5e0 dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/24 12:50 android14-6.1 92668decd5e0 dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/23 21:05 android14-6.1 92668decd5e0 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/23 05:49 android14-6.1 92668decd5e0 881ce5c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/21 12:13 android14-6.1 72b456bf57ad 7c5de9c3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/18 16:49 android14-6.1 c7e15f0bdc49 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/17 22:51 android14-6.1 c7e15f0bdc49 8aaff637 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue
* Struck through repros no longer work on HEAD.