syzbot


KASAN: use-after-free Write in __kernfs_remove

Status: upstream: reported on 2026/06/29 08:38
Reported-by: syzbot+0efffa679f627b85147f@syzkaller.appspotmail.com
First crash: 1d01h, last: 1d01h
Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in __kernfs_remove kernfs 17 4 1670d 1769d 0/29 auto-closed as invalid on 2022/04/02 06:14
upstream KASAN: use-after-free Read in __kernfs_remove 19 C done 3985 1361d 1404d 22/29 fixed on 2023/02/24 13:50
android-5-15 KASAN: null-ptr-deref Write in __kernfs_remove 12 1 723d 723d 0/2 auto-obsoleted due to no activity on 2024/10/04 23:45
upstream KMSAN: uninit-value in __kernfs_remove kernfs 7 1 454d 450d 0/29 auto-obsoleted due to no activity on 2025/07/10 13:09
android-5-10 KASAN: null-ptr-deref Write in __kernfs_remove 12 1 700d 700d 0/2 auto-obsoleted due to no activity on 2024/10/27 11:25

Sample crash report:
bond0 (unregistering): (slave team0): Releasing backup interface
bond0 (unregistering): Released all slaves
bond1 (unregistering): (slave geneve2): Releasing backup interface
bond1 (unregistering): Released all slaves
==================================================================
BUG: KASAN: use-after-free in __rb_erase_augmented include/linux/rbtree_augmented.h:218 [inline]
BUG: KASAN: use-after-free in rb_erase+0x7f4/0xbbc lib/rbtree.c:443
Write of size 8 at addr ffff000000000000 by task kworker/u4:4/1591

CPU: 0 PID: 1591 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/02/2026
Workqueue: netns cleanup_net
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 __asan_report_store8_noabort+0x2c/0x38 mm/kasan/report_generic.c:356
 __rb_erase_augmented include/linux/rbtree_augmented.h:218 [inline]
 rb_erase+0x7f4/0xbbc lib/rbtree.c:443
 kernfs_unlink_sibling fs/kernfs/dir.c:418 [inline]
 __kernfs_remove+0x4bc/0x654 fs/kernfs/dir.c:1467
 kernfs_remove_by_name_ns+0xe4/0x184 fs/kernfs/dir.c:1667
 kernfs_remove_by_name include/linux/kernfs.h:622 [inline]
 remove_files fs/sysfs/group.c:28 [inline]
 sysfs_remove_group+0xf4/0x278 fs/sysfs/group.c:288
 netdev_queue_update_kobjects+0x3b4/0x444 net/core/net-sysfs.c:1729
 remove_queue_kobjects net/core/net-sysfs.c:1828 [inline]
 netdev_unregister_kobject+0xf0/0x204 net/core/net-sysfs.c:1981
 unregister_netdevice_many_notify+0x1300/0x1900 net/core/dev.c:11051
 unregister_netdevice_many net/core/dev.c:11077 [inline]
 default_device_exit_batch+0x9d4/0xa70 net/core/dev.c:11549
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x650/0xa90 net/core/net_namespace.c:640
 process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
 worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
 kthread+0x254/0x2e0 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

The buggy address belongs to the physical page:
page:00000000ceb0d921 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x40000
flags: 0x1ffc00000000000(node=0|zone=0|lastcpupid=0x7ff)
raw: 01ffc00000000000 fffffc0000010008 ffff0001fea6db20 0000000000000000
raw: 0000000000000000 000000000000000a 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
Unable to handle kernel paging request at virtual address ffff5fffffffffe0
KASAN: maybe wild-memory-access in range [0xfffeffffffffff00-0xfffeffffffffff07]
Mem abort info:
  ESR = 0x0000000096000004
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000004
  CM = 0, WnR = 0
swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000020dcd1000
[ffff5fffffffffe0] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 1591 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/02/2026
Workqueue: netns cleanup_net
pstate: 624000c5 (nZCv daIF +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : __memcpy+0x24/0x240 arch/arm64/lib/memcpy.S:71
lr : kasan_metadata_fetch_row+0x20/0x2c mm/kasan/report_generic.c:156
sp : ffff800025a57470
x29: ffff800025a57470 x28: ffff0000cd630cb0 x27: 1fffe0001cc9ac0a
x26: ffff0000e64d6128 x25: dfff800000000000 x24: ffff0000cd630d20
x23: 1fffe0001cc9ac27 x22: fffeffffffffff00 x21: ffff000000000000
x20: ffff000000000000 x19: ffff000000000000 x18: 1fffe00033e7ff7e
x17: 0000000000000000 x16: ffff8000088f3a30 x15: 0000000000000000
x14: 0000000000000001 x13: 1ffff00004b4ae95 x12: 0000000000000000
x11: ff00800011a33250 x10: 0000000000000000 x9 : 64f659dc8615c100
x8 : dfff800000000000 x7 : 0000000000000000 x6 : 000000000000003a
x5 : ffff800025a57498 x4 : ffff5ffffffffff0 x3 : ffff800011a31b94
x2 : 0000000000000010 x1 : ffff5fffffffffe0 x0 : ffff800025a57488
Call trace:
 __memcpy+0x24/0x240 arch/arm64/lib/memcpy.S:70
 print_memory_metadata+0x60/0x310 mm/kasan/report.c:396
 print_report+0x58/0x68 mm/kasan/report.c:421
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 __asan_report_store8_noabort+0x2c/0x38 mm/kasan/report_generic.c:356
 __rb_erase_augmented include/linux/rbtree_augmented.h:218 [inline]
 rb_erase+0x7f4/0xbbc lib/rbtree.c:443
 kernfs_unlink_sibling fs/kernfs/dir.c:418 [inline]
 __kernfs_remove+0x4bc/0x654 fs/kernfs/dir.c:1467
 kernfs_remove_by_name_ns+0xe4/0x184 fs/kernfs/dir.c:1667
 kernfs_remove_by_name include/linux/kernfs.h:622 [inline]
 remove_files fs/sysfs/group.c:28 [inline]
 sysfs_remove_group+0xf4/0x278 fs/sysfs/group.c:288
 netdev_queue_update_kobjects+0x3b4/0x444 net/core/net-sysfs.c:1729
 remove_queue_kobjects net/core/net-sysfs.c:1828 [inline]
 netdev_unregister_kobject+0xf0/0x204 net/core/net-sysfs.c:1981
 unregister_netdevice_many_notify+0x1300/0x1900 net/core/dev.c:11051
 unregister_netdevice_many net/core/dev.c:11077 [inline]
 default_device_exit_batch+0x9d4/0xa70 net/core/dev.c:11549
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x650/0xa90 net/core/net_namespace.c:640
 process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
 worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
 kthread+0x254/0x2e0 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850
Code: f100805f 540003c8 f100405f 540000c3 (a9401c26) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	f100805f 	cmp	x2, #0x20
   4:	540003c8 	b.hi	0x7c  // b.pmore
   8:	f100405f 	cmp	x2, #0x10
   c:	540000c3 	b.cc	0x24  // b.lo, b.ul, b.last
* 10:	a9401c26 	ldp	x6, x7, [x1] <-- trapping instruction

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/29 08:37 linux-6.1.y fdb6fcb41cc7 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in __kernfs_remove
* Struck through repros no longer work on HEAD.