[BUG] ata: pata_parport: KASAN slab-use-after-free in driver_find

[Shuangpeng Bai]

Hi Kernel Maintainers,

I hit the following report while testing current upstream kernel:

KASAN: slab-use-after-free in driver_find

on commit: 62efbc768363bc7bb00f0915ad265f34b40d414e (2026-07-27)

To help trigger the bug more reliably, we applied a minimal diagnostic patch
that only adds a delay.

The reproducer and .config files are here.
https://gist.github.com/shuangpengbai/a8a1b5339bc41944c2f80d9f87e01a7e

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

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

[  755.753286][ T8297] BUG: KASAN: slab-use-after-free in driver_find (drivers/base/bus.c:1430)
[  755.754175][ T8297] Read of size 8 at addr ffff88812200f490 by task repro.sh/8297
[  755.755320][ T8297] 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
[  755.755331][ T8297] Call Trace:
[  755.755341][ T8297]  <TASK>
[  755.755344][ T8297]  dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
[  755.755393][ T8297]  print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
[  755.755478][ T8297]  kasan_report (mm/kasan/report.c:595)
[  755.755487][ T8297]  driver_find (drivers/base/bus.c:1430)
[  755.755502][ T8297]  new_device_store (drivers/ata/pata_parport/pata_parport.c:649)
[  755.755610][ T8297]  kernfs_fop_write_iter (fs/kernfs/file.c:345)
[  755.755615][ T8297]  vfs_write (fs/read_write.c:595 fs/read_write.c:687)
[  755.755678][ T8297]  ksys_write (fs/read_write.c:739)
[  755.755703][ T8297]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[  755.755717][ T8297]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
[  755.779923][ T8297] Freed by task 8297 on cpu 0 at 755.752571s:
[  755.780598][ T8297]  kasan_save_track (mm/kasan/common.c:57 mm/kasan/common.c:78)
[  755.781128][ T8297]  kasan_save_free_info (mm/kasan/generic.c:584)
[  755.781700][ T8297]  __kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)
[  755.782222][ T8297]  kfree (./include/linux/kasan.h:235 mm/slub.c:2705 mm/slub.c:6405 mm/slub.c:6720)
[  755.782658][ T8297]  kobject_put (lib/kobject.c:689 lib/kobject.c:720 ./include/linux/kref.h:65 lib/kobject.c:737)
[  755.783163][ T8297]  driver_find (drivers/base/bus.c:1429)
[  755.783659][ T8297]  new_device_store (drivers/ata/pata_parport/pata_parport.c:649)
[  755.787092][ T8297] The buggy address belongs to the object at ffff88812200f400
[  755.787092][ T8297]  which belongs to the cache kmalloc-192 of size 192
[  755.788598][ T8297] The buggy address is located 144 bytes inside of
[  755.788598][ T8297]  freed 192-byte region [ffff88812200f400, ffff88812200f4c0)

Best,
Shuangpeng