KASAN: use-after-free Read in rcu_cblist_dequeue

Status: upstream: reported C repro on 2026/06/11 16:19
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+9da04cc1c19a8165b176@syzkaller.appspotmail.com
First crash: 67d, last: 6h32m
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/06/16 lts (merge base) ad16b162f21d C [report] lost connection to test machine
2026/06/16 upstream (ToT) 481329ec5b31 C [report] lost connection to test machine
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in rcu_cblist_dequeue kernel 19 1 3050d 3050d 0/29 closed as invalid on 2018/04/12 23:01
android-5-10 KASAN: use-after-free Read in rcu_cblist_dequeue (2) 19 syz, C 388 1h05m 56d 0/2 upstream: reported C repro on 2026/06/22 21:37
android-5-10 KASAN: use-after-free Read in rcu_cblist_dequeue 19 1 1755d 1749d 0/2 auto-closed as invalid on 2022/02/24 12:16
android-5-15 KASAN: use-after-free Read in rcu_cblist_dequeue origin:upstream 19 syz, C 124 2h25m 50d 0/2 upstream: reported C repro on 2026/06/28 12:44
upstream BUG: unable to handle kernel paging request in rcu_cblist_dequeue rcu 8 6 350d 354d 0/29 auto-obsoleted due to no activity on 2025/12/10 12:07
upstream KASAN: slab-use-after-free Read in rcu_cblist_dequeue crypto 19 1 232d 228d 0/29 auto-obsoleted due to no activity on 2026/03/28 00:06

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888112d47190 by task ksoftirqd/1/23

CPU: 1 PID: 23 Comm: ksoftirqd/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351
 rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
 rcu_do_batch+0x4bc/0xc30 kernel/rcu/tree.c:2285
 rcu_core+0x486/0xf00 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+0x48c/0x8e0 kernel/smpboot.c:164
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Allocated by task 373:
 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 10:
 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 ffff888112d47000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff888112d47000, ffff888112d47200)

The buggy address belongs to the physical page:
page:ffffea00044b5100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112d44
head:ffffea00044b5100 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00044ad100 dead000000000002 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 111, tgid 111 (udevd), ts 6071507442, 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_node_track_caller+0xa1/0x1e0 mm/slab_common.c:958
 kmalloc_reserve net/core/skbuff.c:449 [inline]
 __alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
 alloc_skb include/linux/skbuff.h:1322 [inline]
 alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6176
 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2761
 unix_dgram_sendmsg+0x5c1/0x1710 net/unix/af_unix.c:1947
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 sock_write_iter+0x2ea/0x3f0 net/socket.c:1133
 call_write_iter include/linux/fs.h:2282 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ef/0xd00 fs/read_write.c:584
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888112d47080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888112d47100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888112d47180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888112d47200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888112d47280: fc fc fc fc fc

Crashes (395):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/08 14:13 android14-6.1 92668decd5e0 5d63f80b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/04 12:33 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 Read in rcu_cblist_dequeue
2026/08/04 07:52 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 Read in rcu_cblist_dequeue
2026/08/04 07:02 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 Read in rcu_cblist_dequeue
2026/08/04 06:32 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 Read in rcu_cblist_dequeue
2026/07/27 10:21 android14-6.1 92668decd5e0 492bab15 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/06/22 03:36 android14-6.1 72813af230c7 43bfcdb0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/06/11 16:07 android14-6.1 bf32db543281 d93a6ab6 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/02 17:54 android14-6.1 92668decd5e0 e611ffe1 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/17 17:32 android14-6.1 92668decd5e0 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/17 12:58 android14-6.1 92668decd5e0 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/17 11:32 android14-6.1 92668decd5e0 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/17 02:50 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/17 01:48 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/17 00:19 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/16 23:04 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/16 18:52 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/16 13:21 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/16 11:35 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/16 06:11 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/16 03:16 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/16 02:01 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/15 18:47 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/15 15:57 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/15 14:18 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/15 12:25 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/15 10:52 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/15 01:37 android14-6.1 92668decd5e0 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/14 12:45 android14-6.1 92668decd5e0 6f9b3e89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/14 08:03 android14-6.1 92668decd5e0 b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/14 05:22 android14-6.1 92668decd5e0 b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/13 19:56 android14-6.1 92668decd5e0 b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/13 18:37 android14-6.1 92668decd5e0 b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/13 18:37 android14-6.1 92668decd5e0 b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/13 15:53 android14-6.1 92668decd5e0 359b2492 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/13 14:29 android14-6.1 92668decd5e0 359b2492 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/12 19:11 android14-6.1 92668decd5e0 359b2492 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/12 17:31 android14-6.1 92668decd5e0 f8d35649 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/12 02:38 android14-6.1 92668decd5e0 f8d35649 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/11 18:59 android14-6.1 92668decd5e0 71790083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/11 13:56 android14-6.1 92668decd5e0 71790083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/11 11:34 android14-6.1 92668decd5e0 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/11 10:12 android14-6.1 92668decd5e0 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/10 20:41 android14-6.1 92668decd5e0 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/10 20:32 android14-6.1 92668decd5e0 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/10 15:07 android14-6.1 92668decd5e0 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/10 10:35 android14-6.1 92668decd5e0 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/09 20:46 android14-6.1 92668decd5e0 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/09 13:44 android14-6.1 92668decd5e0 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/09 05:43 android14-6.1 92668decd5e0 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/08 04:41 android14-6.1 92668decd5e0 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/08 02:55 android14-6.1 92668decd5e0 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/08/07 22:51 android14-6.1 92668decd5e0 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
2026/06/11 02:03 android14-6.1 bf32db543281 b754d2d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in rcu_cblist_dequeue
* Struck through repros no longer work on HEAD.