KASAN: use-after-free Write in rcu_segcblist_enqueue

Status: upstream: reported C repro on 2026/06/22 22:11
Reported-by: syzbot+c103c1bbd97dad306fc9@syzkaller.appspotmail.com
First crash: 50d, last: 1d03h
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Write in rcu_segcblist_enqueue 22 syz, C 176 6h46m 58d 0/2 upstream: reported C repro on 2026/06/14 23:49
android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue origin:upstream 22 syz, C 39 1d18h 44d 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 1800d 1865d 20/29 fixed on 2022/03/08 16:11

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in rcu_segcblist_enqueue+0x4b/0xa0 kernel/rcu/rcu_segcblist.c:249
Write of size 8 at addr ffff88811127a190 by task syz.2.17/369

CPU: 0 PID: 369 Comm: syz.2.17 Not tainted 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:77
 dump_stack_lvl+0x1a7/0x208 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+0x100/0x140 mm/kasan/report.c:452
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report_generic.c:314
 rcu_segcblist_enqueue+0x4b/0xa0 kernel/rcu/rcu_segcblist.c:249
 __call_rcu kernel/rcu/tree.c:2998 [inline]
 call_rcu+0x4df/0x1090 kernel/rcu/tree.c:3054
 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
 __sock_release net/socket.c:597 [inline]
 sock_close+0xb8/0x200 net/socket.c:1287
 __fput+0x2dc/0x730 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
RIP: 0033:0x7fefa797fe99
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:00007ffc7cae8b38 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffc7cae8c20 RCX: 00007fefa797fe99
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000005fda R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32c20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fefa7c07fac R14: 00007fefa7c07fa8 R15: 00007fefa7c07fa0

Allocated by task 369:
 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+0xd4/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 __kmalloc+0x19f/0x330 mm/slub.c:4038
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
 __sys_connect_file net/socket.c:1867 [inline]
 __sys_connect+0x3ce/0x450 net/socket.c:1884
 __do_sys_connect net/socket.c:1894 [inline]
 __se_sys_connect net/socket.c:1891 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1891
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 49:
 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_put+0xb2/0x1a0 net/l2tp/l2tp_core.c:193
 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline]
 l2tp_tunnel_del_work+0x180/0x3d0 net/l2tp/l2tp_core.c:1273
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

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+0x11a/0x1090 kernel/rcu/tree.c:3054
 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
 __sock_release net/socket.c:597 [inline]
 sock_close+0xb8/0x200 net/socket.c:1287
 __fput+0x2dc/0x730 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 ffff88811127a000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff88811127a000, ffff88811127a200)
The buggy address belongs to the page:
page:ffffea0004449e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x111278
head:ffffea0004449e00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea00043e9500 0000000500000005 ffff888100043080
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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 98, ts 4140207263, 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+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 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+0x2f8/0x4c0 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+0x1e4/0x310 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+0xa3/0x560 net/core/skbuff.c:6006
 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2393
 unix_dgram_sendmsg+0x6f3/0x18f0 net/unix/af_unix.c:1725
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 sock_write_iter+0x2a6/0x3a0 net/socket.c:1019
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x770/0xd70 fs/read_write.c:605
 ksys_write+0x14a/0x260 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:
 ffff88811127a080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811127a100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811127a180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88811127a200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88811127a280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (122):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/21 13:10 android13-5.10-lts 50b3a256e550 7c5de9c3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/22 22:00 android13-5.10-lts 72aefab72b3d 5a630be6 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/26 08:48 android13-5.10-lts 79e905dd56a7 7ff32d8b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/11 10:02 android13-5.10-lts dce28bf8c73c 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/10 22:37 android13-5.10-lts 447db0046f21 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/10 15:31 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/10 13:14 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/10 07:14 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/09 21:41 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/09 11:21 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/09 08:38 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/09 00:56 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/08 22:54 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/08 21:41 android13-5.10-lts 447db0046f21 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/06 12:18 android13-5.10-lts 0f73d4924a74 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/06 09:58 android13-5.10-lts 0f73d4924a74 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/05 13:31 android13-5.10-lts 0f73d4924a74 52aa2820 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/05 09:04 android13-5.10-lts 0f73d4924a74 52aa2820 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/04 20:21 android13-5.10-lts 0f73d4924a74 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/04 12:44 android13-5.10-lts 0f73d4924a74 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/04 12:44 android13-5.10-lts 0f73d4924a74 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/04 07:28 android13-5.10-lts 0f73d4924a74 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/08/02 09:49 android13-5.10-lts 50b3a256e550 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/26 23:09 android13-5.10-lts 50b3a256e550 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/26 16:19 android13-5.10-lts 50b3a256e550 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/26 02:16 android13-5.10-lts 50b3a256e550 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 19:35 android13-5.10-lts 50b3a256e550 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 09:07 android13-5.10-lts 50b3a256e550 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/25 02:31 android13-5.10-lts 50b3a256e550 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/24 17:00 android13-5.10-lts 50b3a256e550 dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/24 09:26 android13-5.10-lts 50b3a256e550 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/23 14:31 android13-5.10-lts 50b3a256e550 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/22 05:01 android13-5.10-lts 50b3a256e550 b561ce9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/21 20:36 android13-5.10-lts 50b3a256e550 7c5de9c3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/21 08:53 android13-5.10-lts 50b3a256e550 de6a700d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/18 23:03 android13-5.10-lts 50b3a256e550 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/18 19:03 android13-5.10-lts 50b3a256e550 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/18 11:04 android13-5.10-lts 50b3a256e550 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/18 00:28 android13-5.10-lts 50b3a256e550 8aaff637 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/17 10:50 android13-5.10-lts 50b3a256e550 7f27c57a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/16 10:41 android13-5.10-lts 50b3a256e550 27a8bd60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/15 21:47 android13-5.10-lts 50b3a256e550 a4ed0f4f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/15 17:36 android13-5.10-lts 50b3a256e550 a4ed0f4f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/14 22:49 android13-5.10-lts 50b3a256e550 2130f682 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/14 14:50 android13-5.10-lts 50b3a256e550 2130f682 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/14 09:50 android13-5.10-lts 50b3a256e550 2130f682 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/22 18:49 android13-5.10-lts 72aefab72b3d 5a630be6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue
* Struck through repros no longer work on HEAD.