KASAN: use-after-free Write in rcu_segcblist_enqueue

Status: upstream: reported C repro on 2026/06/29 08:43
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+ce5d0a26f87b6323905b@syzkaller.appspotmail.com
First crash: 32d, last: 2d20h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/07/01 lts (merge base) 64ee49df839f C [report] lost connection to test machine
2026/07/01 upstream (ToT) 665159e24674 C [report] lost connection to test machine
▶ ▼ 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 C 101 31m 39d 0/2 upstream: reported C repro on 2026/06/14 23:49
android-5-10 KASAN: use-after-free Write in rcu_segcblist_enqueue 22 C 91 3h08m 31d 0/2 upstream: reported C repro on 2026/06/22 22:11
upstream general protection fault in rcu_segcblist_enqueue kvm-x86 2 C done done 368 1782d 1846d 20/29 fixed on 2022/03/08 16:11

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in rcu_segcblist_enqueue+0x9c/0xb0 kernel/rcu/rcu_segcblist.c:348
Write of size 8 at addr ffff88811dd73190 by task syz.2.17/371

CPU: 0 PID: 371 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 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+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report_generic.c:314
 rcu_segcblist_enqueue+0x9c/0xb0 kernel/rcu/rcu_segcblist.c:348
 __call_rcu_common kernel/rcu/tree.c:3030 [inline]
 call_rcu+0x549/0xf60 kernel/rcu/tree.c:3129
 security_inode_free+0xb4/0xd0 security/security.c:1066
 __destroy_inode+0x175/0x4f0 fs/inode.c:289
 destroy_inode fs/inode.c:312 [inline]
 evict+0x769/0x8b0 fs/inode.c:665
 iput_final fs/inode.c:1779 [inline]
 iput+0x651/0x7e0 fs/inode.c:1805
 dentry_unlink_inode+0x338/0x3e0 fs/dcache.c:380
 __dentry_kill+0x45b/0x660 fs/dcache.c:586
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x47/0x90 fs/dcache.c:893
 __fput+0x5c7/0x900 fs/file_table.c:319
 ____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+0x87/0xd0 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
RIP: 0033:0x7fbdb74a2e59
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:00007fffbc2c4da8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fffbc2c4e90 RCX: 00007fbdb74a2e59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000066a8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32d20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbdb772afac R14: 00007fbdb772afa8 R15: 00007fbdb772afa0
 </TASK>

Allocated by task 371:
 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+0xd4/0x100 mm/kasan/common.c:521
 kasan_kmalloc include/linux/kasan.h:227 [inline]
 __kmalloc+0x13d/0x2c0 mm/slub.c:4436
 kmalloc include/linux/slab.h:624 [inline]
 kzalloc include/linux/slab.h:750 [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:1922 [inline]
 __sys_connect+0x3cb/0x450 net/socket.c:1939
 __do_sys_connect net/socket.c:1949 [inline]
 __se_sys_connect net/socket.c:1946 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1946
 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 45:
 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:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kfree+0xc4/0x270 mm/slub.c:4588
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_put+0xaf/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+0x6c8/0xbb0 kernel/workqueue.c:2328
 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475
 kthread+0x3f5/0x4f0 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

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:3011 [inline]
 call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
 __sock_release net/socket.c:649 [inline]
 sock_close+0xb8/0x200 net/socket.c:1335
 __fput+0x22b/0x900 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+0x87/0xd0 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 ffff88811dd73000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff88811dd73000, ffff88811dd73200)
The buggy address belongs to the page:
page:ffffea0004775c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11dd70
head:ffffea0004775c00 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 371, ts 26300828251, free_ts 25213483363
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa0/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 __kmalloc+0x16a/0x2c0 mm/slub.c:4432
 kmalloc include/linux/slab.h:624 [inline]
 kzalloc include/linux/slab.h:750 [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:1922 [inline]
 __sys_connect+0x3cb/0x450 net/socket.c:1939
 __do_sys_connect net/socket.c:1949 [inline]
 __se_sys_connect net/socket.c:1946 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1946
 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
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1474 [inline]
 free_pcp_prepare mm/page_alloc.c:1546 [inline]
 free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
 free_unref_page+0xae/0x540 mm/page_alloc.c:3618
 free_the_page mm/page_alloc.c:805 [inline]
 __free_pages+0x6c/0x100 mm/page_alloc.c:5900
 __vunmap+0x801/0x980 mm/vmalloc.c:2660
 __vfree mm/vmalloc.c:2709 [inline]
 vfree+0x8b/0xc0 mm/vmalloc.c:2740
 kcov_put kernel/kcov.c:417 [inline]
 kcov_close+0x2b/0x50 kernel/kcov.c:519
 __fput+0x22b/0x900 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+0xb70/0x29a0 kernel/exit.c:890
 do_group_exit+0x149/0x310 kernel/exit.c:1004
 get_signal+0x64f/0x1430 kernel/signal.c:2907
 arch_do_signal_or_restart+0xe2/0x1100 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0x87/0xd0 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

Memory state around the buggy address:
 ffff88811dd73080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811dd73100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811dd73180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88811dd73200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88811dd73280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (29):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/07 18:30 android13-5.15-lts 5c01a18cdaee 76cdc0c0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/07 06:33 android13-5.15-lts 2ceba11ffa52 8e71ce95 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/29 08:33 android13-5.15-lts c85054db4618 fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/03 18:27 android13-5.15-lts a64de05eba09 58bf2096 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/22 00:19 android13-5.15-lts 61d896ee2a80 b561ce9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/19 05:36 android13-5.15-lts 31c263582f4e 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/16 00:59 android13-5.15-lts 31c263582f4e 27a8bd60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/16 00:59 android13-5.15-lts 31c263582f4e 27a8bd60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/13 13:25 android13-5.15-lts e193e88d68f2 cc4833d0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/11 11:58 android13-5.15-lts 0a85a2bd13c2 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/08 12:31 android13-5.15-lts 5c01a18cdaee 88a4b44c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/06 04:27 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/05 16:08 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/05 04:46 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/05 04:42 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/05 04:42 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/04 16:41 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/04 14:59 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/04 07:56 android13-5.15-lts a64de05eba09 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/07/01 01:46 android13-5.15-lts c85054db4618 00e8b0fd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/29 08:15 android13-5.15-lts c85054db4618 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/29 07:04 android13-5.15-lts c85054db4618 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/29 06:36 android13-5.15-lts c85054db4618 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/29 01:07 android13-5.15-lts c85054db4618 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/28 16:40 android13-5.15-lts c85054db4618 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/28 04:47 android13-5.15-lts c85054db4618 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/25 16:34 android13-5.15-lts c85054db4618 cfa969bf .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/24 23:40 android13-5.15-lts c85054db4618 302586aa .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
2026/06/22 14:14 android13-5.15-lts 7ad09e849dbe 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in rcu_segcblist_enqueue
* Struck through repros no longer work on HEAD.