[BUG] PCI/VGA: KASAN slab-use-after-free in dev_driver_string from vga_arb_release

[Shuangpeng <shuangpeng.kernel@gmail.com>]

Hi Kernel Maintainers,

I hit the following report while testing current upstream kernel:

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

on commit: e8c2f9fdadee7cbc75134dc463c1e0d856d6e5c7 (May 25 2026)

The reproducer and .config files are here.
https://gist.github.com/shuangpengbai/47ec0715a0120beaacf5009460b90687

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

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

[  250.268327][ T8342] ==================================================================
[  250.271034][ T8342] BUG: KASAN: slab-use-after-free in dev_driver_string (drivers/base/core.c:2406)
[  250.273371][ T8342] Read of size 8 at addr ffff88810aebc138 by task bash/8342
[  250.274604][ T8342]
[  250.275019][ T8342] CPU: 0 UID: 0 PID: 8342 Comm: bash Not tainted 7.1.0-rc5+ #106 PREEMPT(full)
[  250.275027][ T8342] 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
[  250.275031][ T8342] Call Trace:
[  250.275044][ T8342]  <TASK>
[  250.275049][ T8342]  dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
[  250.275108][ T8342]  print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
[  250.275177][ T8342]  kasan_report (mm/kasan/report.c:595)
[  250.275190][ T8342]  dev_driver_string (drivers/base/core.c:2406)
[  250.275196][ T8342]  __dynamic_dev_dbg (lib/dynamic_debug.c:906)
[  250.275228][ T8342]  vga_arb_release (drivers/pci/vgaarb.c:1436)
[  250.275245][ T8342]  __fput (fs/file_table.c:510)
[  250.275260][ T8342]  fput_close_sync (fs/file_table.c:615)
[  250.275265][ T8342]  __x64_sys_close (fs/open.c:1507 fs/open.c:1492 fs/open.c:1492)
[  250.275271][ T8342]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[  250.275327][ T8342]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
[  250.275333][ T8342] RIP: 0033:0x7f65140dbc03
[  250.275341][ T8342] 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
[  250.275346][ T8342] RSP: 002b:00007ffce08e3808 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[  250.275363][ T8342] RAX: ffffffffffffffda RBX: 0000564bd1808ba0 RCX: 00007f65140dbc03
[  250.275367][ T8342] RDX: 00000000ffffffff RSI: 0000000000000001 RDI: 000000000000000a
[  250.275371][ T8342] RBP: 00007ffce08e3890 R08: 0000000000000000 R09: 0000000000000000
[  250.275374][ T8342] R10: 00007f651417efc0 R11: 0000000000000246 R12: 0000000000000009
[  250.275377][ T8342] R13: 0000000000000009 R14: 000000000000000a R15: 0000000000000000
[  250.275393][ T8342]  </TASK>
[  250.275395][ T8342]
[  250.295059][ T8342] Freed by task 8342 on cpu 1 at 249.233016s:
[  250.295689][ T8342]  kasan_save_track (mm/kasan/common.c:57 mm/kasan/common.c:78)
[  250.296168][ T8342]  kasan_save_free_info (mm/kasan/generic.c:584)
[  250.296682][ T8342]  __kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)
[  250.297176][ T8342]  kfree (include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6251 mm/slub.c:6566)
[  250.297593][ T8342]  device_release (drivers/base/core.c:2570)
[  250.298062][ T8342]  kobject_put (lib/kobject.c:689 lib/kobject.c:720 include/linux/kref.h:65 lib/kobject.c:737)
[  250.298528][ T8342]  pci_stop_and_remove_bus_device_locked (drivers/pci/remove.c:132 drivers/pci/remove.c:139)
[  250.299187][ T8342]  remove_store (drivers/pci/pci-sysfs.c:525)
[  250.299631][ T8342]  kernfs_fop_write_iter (fs/kernfs/file.c:352)
[  250.300179][ T8342]  vfs_write (fs/read_write.c:595 fs/read_write.c:688)
[  250.300622][ T8342]  ksys_write (fs/read_write.c:740)
[  250.301054][ T8342]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[  250.301525][ T8342]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
[  250.302121][ T8342]
[  250.302372][ T8342] The buggy address belongs to the object at ffff88810aebc000
[  250.302372][ T8342]  which belongs to the cache kmalloc-4k of size 4096
[  250.303772][ T8342] The buggy address is located 312 bytes inside of
[  250.303772][ T8342]  freed 4096-byte region [ffff88810aebc000, ffff88810aebd000)
[  250.305161][ T8342]

Best,
Shuangpeng