[BUG] KASAN: slab-use-after-free in dev_driver_string from chaoskey_release

[Shuangpeng]

Hi Kernel Maintainers,

I hit the following KASAN report while testing current upstream kernel:

KASAN: slab-use-after-free in dev_driver_string from chaoskey_release

on commit: e8c2f9fdadee7cbc75134dc463c1e0d856d6e5c7 (May 25 2026)

The reproducer and .config files are here.
https://gist.github.com/shuangpengbai/167620d391d9634107bfe4d784fcf52b

I’m happy to test debug patches or provide additional information.

Reported-by: Shuangpeng Bai <shuangpeng.kernel@xxxxxxxxx>


[ 2019.816807][T10106] ==================================================================
[ 2019.819081][T10106] BUG: KASAN: slab-use-after-free in dev_driver_string (drivers/base/core.c:2406)
[ 2019.820996][T10106] Read of size 8 at addr ffff888168e8a0b8 by task chaoskey_raw_re/10106
[ 2019.822432][T10106]
[ 2019.822899][T10106] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 2019.822904][T10106] Call Trace:
[ 2019.822910][T10106]  <TASK>
[ 2019.822915][T10106]  dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
[ 2019.822932][T10106]  print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
[ 2019.822984][T10106]  kasan_report (mm/kasan/report.c:595)
[ 2019.823015][T10106]  dev_driver_string (drivers/base/core.c:2406)
[ 2019.823021][T10106]  __dynamic_dev_dbg (lib/dynamic_debug.c:906)
[ 2019.823282][T10106]  chaoskey_release (drivers/usb/misc/chaoskey.c:323)
[ 2019.823290][T10106]  __fput (fs/file_table.c:510)
[ 2019.823298][T10106]  fput_close_sync (fs/file_table.c:615)
[ 2019.823320][T10106]  __x64_sys_close (fs/open.c:1507 fs/open.c:1492 fs/open.c:1492)
[ 2019.823327][T10106]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[ 2019.823337][T10106]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
[ 2019.823344][T10106] RIP: 0033:0x7f52411ffc03
[ 2019.823352][T10106] Code: e9 37 ff ff ff e8 2d f9 01 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8
All code
========
   0:	e9 37 ff ff ff       	jmp    0xffffffffffffff3c
   5:	e8 2d f9 01 00       	call   0x1f937
   a:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  11:	00 00 00 
  14:	0f 1f 00             	nopl   (%rax)
  17:	64 8b 04 25 18 00 00 	mov    %fs:0x18,%eax
  1e:	00 
  1f:	85 c0                	test   %eax,%eax
  21:	75 14                	jne    0x37
  23:	b8 03 00 00 00       	mov    $0x3,%eax
  28:	0f 05                	syscall
  2a:*	48 3d 00 f0 ff ff    	cmp    $0xfffffffffffff000,%rax		<-- trapping instruction
  30:	77 45                	ja     0x77
  32:	c3                   	ret
  33:	0f 1f 40 00          	nopl   0x0(%rax)
  37:	48 83 ec 18          	sub    $0x18,%rsp
  3b:	89 7c 24 0c          	mov    %edi,0xc(%rsp)
  3f:	e8                   	.byte 0xe8

Code starting with the faulting instruction
===========================================
   0:	48 3d 00 f0 ff ff    	cmp    $0xfffffffffffff000,%rax
   6:	77 45                	ja     0x4d
   8:	c3                   	ret
   9:	0f 1f 40 00          	nopl   0x0(%rax)
   d:	48 83 ec 18          	sub    $0x18,%rsp
  11:	89 7c 24 0c          	mov    %edi,0xc(%rsp)
  15:	e8                   	.byte 0xe8
[ 2019.823358][T10106] RSP: 002b:00007ffd4b423688 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[ 2019.823382][T10106] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f52411ffc03
[ 2019.823388][T10106] RDX: 0000000000000000 RSI: 00007ffd4b421570 RDI: 0000000000000003
[ 2019.823400][T10106] RBP: 00007ffd4b423af0 R08: 00007f52412a3040 R09: 00007f52412a30c0
[ 2019.823404][T10106] R10: fffffffffffff639 R11: 0000000000000246 R12: 00007ffd4b4238f0
[ 2019.823408][T10106] R13: 0000000000000003 R14: 0000000000000000 R15: 000000000000277c
[ 2019.823417][T10106]  </TASK>
[ 2019.823420][T10106]
[ 2019.842033][T10106] Freed by task 10106 on cpu 0 at 2019.816700s:
[ 2019.842461][T10106]  kasan_save_track (mm/kasan/common.c:57 mm/kasan/common.c:78)
[ 2019.842793][T10106]  kasan_save_free_info (mm/kasan/generic.c:584)
[ 2019.843137][T10106]  __kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)
[ 2019.843463][T10106]  kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6251 mm/slub.c:6566)
[ 2019.843736][T10106]  device_release (drivers/base/core.c:2562)
[ 2019.844053][T10106]  kobject_put (lib/kobject.c:689 lib/kobject.c:720 ./include/linux/kref.h:65 lib/kobject.c:737)
[ 2019.844368][T10106]  chaoskey_free (drivers/usb/misc/chaoskey.c:103)
[ 2019.844696][T10106]  chaoskey_release (drivers/usb/misc/chaoskey.c:315)
[ 2019.845038][T10106]  __fput (fs/file_table.c:510)
[ 2019.845322][T10106]  fput_close_sync (fs/file_table.c:615)
[ 2019.845651][T10106]  __x64_sys_close (fs/open.c:1507 fs/open.c:1492 fs/open.c:1492)
[ 2019.845981][T10106]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[ 2019.846302][T10106]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
[ 2019.846708][T10106]
[ 2019.846874][T10106] The buggy address belongs to the object at ffff888168e8a000
[ 2019.846874][T10106]  which belongs to the cache kmalloc-1k of size 1024
[ 2019.847827][T10106] The buggy address is located 184 bytes inside of
[ 2019.847827][T10106]  freed 1024-byte region [ffff888168e8a000, ffff888168e8a400)


Best,
Shuangpeng