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

[Damien Le Moal <dlemoal@kernel.org>]

On 7/28/26 11:40, Shuangpeng Bai wrote:
> 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.

Can you share that patch/diff? That would make it easier to figure out where the
race is because you are not describing anything here. The stack trace helps, but
without being able to reproduce (I do not have the hardware), this will be hard
to fix.

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

This site has a broken certificate and Firefox does not want (rightly so) to get
me there. So not touching this.

> 
> I'm happy to test debug patches or provide additional information.
> 
> Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
> 
> [  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


-- 
Damien Le Moal
Western Digital Research