KASAN: slab-use-after-free Read in attach_store

Status: moderation: reported on 2026/08/06 10:51
Subsystems: usb
[Documentation on labels]
Reported-by: syzbot+21270bc4bd8a18bbfa06@syzkaller.appspotmail.com
First crash: 4d21h, last: 4d21h
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ID Workflow Result Correct Bug Created Started Finished Revision
737ac415 assessment-security 💥 KASAN: slab-use-after-free Read in attach_store 2026/08/04 01:04 2026/08/04 01:04 2026/08/04 01:04 cb1adeae

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in __mutex_lock_common kernel/locking/mutex.c:625 [inline]
BUG: KASAN: slab-use-after-free in __mutex_lock+0x15ca/0x1bd0 kernel/locking/mutex.c:821
Read of size 8 at addr ffff8880265804f8 by task syz.0.4003/20094

CPU: 1 UID: 0 PID: 20094 Comm: syz.0.4003 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 __mutex_lock_common kernel/locking/mutex.c:625 [inline]
 __mutex_lock+0x15ca/0x1bd0 kernel/locking/mutex.c:821
 attach_store+0x333/0x8f0 drivers/usb/usbip/vhci_sysfs.c:364
 dev_attr_store+0x58/0x80 drivers/base/core.c:2505
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 do_int80_emulation+0x14b/0x720 arch/x86/entry/syscall_32.c:172
 asm_int80_emulation+0x1a/0x20 arch/x86/include/asm/idtentry.h:598
RIP: 0023:0xf71d73eb
Code: 57 56 53 8b 44 24 14 f6 00 08 75 23 8b 44 24 18 8b 5c 24 1c 8b 4c 24 20 8b 54 24 24 8b 74 24 28 8b 7c 24 2c 8b 6c 24 30 cd 80 <5b> 5e 5f 5d c3 5b 5e 5f 5d e9 f7 a1 ff ff 66 90 66 90 66 90 90 53
RSP: 002b:00000000f5453f9c EFLAGS: 00000246 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 000000000000000a RCX: 00000000f5454060
RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 1:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5334 [inline]
 __kmalloc_noprof+0x322/0x820 mm/slub.c:5359
 _kmalloc_noprof include/linux/slab.h:992 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 __usb_create_hcd+0x5e/0xac0 drivers/usb/core/hcd.c:2566
 vhci_hcd_probe+0x1a5/0x4e0 drivers/usb/usbip/vhci_hcd.c:1394
 platform_probe+0x106/0x1d0 drivers/base/platform.c:1439
 call_driver_probe drivers/base/dd.c:628 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:706
 __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
 __device_attach_driver+0x1df/0x320 drivers/base/dd.c:1026
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1098
 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x64/0x160 drivers/base/bus.c:620
 device_add+0x121d/0x1970 drivers/base/core.c:3772
 platform_device_add+0x35a/0x800 drivers/base/platform.c:762
 platform_device_register_full+0x5cf/0x830 drivers/base/platform.c:902
 vhci_hcd_init+0x1a1/0x2f0 drivers/usb/usbip/vhci_hcd.c:1557
 do_one_initcall+0x11d/0x700 init/main.c:1347
 do_initcall_level init/main.c:1409 [inline]
 do_initcalls init/main.c:1425 [inline]
 do_basic_setup init/main.c:1445 [inline]
 kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
 kernel_init+0x1f/0x1e0 init/main.c:1548
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 20088:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kfree+0x22b/0x6c0 mm/slub.c:6692
 hcd_release drivers/usb/core/hcd.c:2690 [inline]
 kref_put include/linux/kref.h:65 [inline]
 usb_put_hcd drivers/usb/core/hcd.c:2704 [inline]
 usb_put_hcd+0x149/0x1f0 drivers/usb/core/hcd.c:2701
 vhci_hcd_remove+0xb5/0x1b0 drivers/usb/usbip/vhci_hcd.c:1431
 platform_remove+0x5f/0x80 drivers/base/platform.c:1456
 device_remove+0xcb/0x180 drivers/base/dd.c:616
 __device_release_driver drivers/base/dd.c:1349 [inline]
 device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
 unbind_store+0xf8/0x110 drivers/base/bus.c:244
 drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Last potentially related work creation:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:556
 insert_work+0x36/0x230 kernel/workqueue.c:2226
 __queue_work+0x9bc/0x12b0 kernel/workqueue.c:2401
 queue_work_on+0x1a9/0x1e0 kernel/workqueue.c:2452
 queue_work include/linux/workqueue.h:699 [inline]
 usb_hcd_giveback_urb+0x330/0x4a0 drivers/usb/core/hcd.c:1758
 usb_rh_urb_dequeue drivers/usb/core/hcd.c:845 [inline]
 unlink1+0x418/0x510 drivers/usb/core/hcd.c:1580
 usb_hcd_unlink_urb+0x131/0x210 drivers/usb/core/hcd.c:1617
 usb_kill_urb drivers/usb/core/urb.c:716 [inline]
 usb_kill_urb+0x121/0x320 drivers/usb/core/urb.c:703
 hub_quiesce+0x1e9/0x320 drivers/usb/core/hub.c:1412
 hub_suspend+0x4ab/0x9e0 drivers/usb/core/hub.c:4008
 usb_suspend_interface drivers/usb/core/driver.c:1323 [inline]
 usb_suspend_both+0x288/0x950 drivers/usb/core/driver.c:1446
 usb_runtime_suspend+0x49/0x120 drivers/usb/core/driver.c:2000
 __rpm_callback+0xc8/0x620 drivers/base/power/runtime.c:406
 rpm_callback+0x16a/0x1b0 drivers/base/power/runtime.c:460
 rpm_suspend+0x2f4/0x11a0 drivers/base/power/runtime.c:698
 __pm_runtime_suspend+0xba/0x1a0 drivers/base/power/runtime.c:1167
 pm_runtime_autosuspend include/linux/pm_runtime.h:415 [inline]
 usb_runtime_idle+0x7e/0x90 drivers/usb/core/driver.c:2037
 rpm_idle+0x322/0x790 drivers/base/power/runtime.c:550
 pm_runtime_work+0x120/0x150 drivers/base/power/runtime.c:995
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Second to last potentially related work creation:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:556
 insert_work+0x36/0x230 kernel/workqueue.c:2226
 __queue_work+0x9bc/0x12b0 kernel/workqueue.c:2401
 queue_work_on+0x1a9/0x1e0 kernel/workqueue.c:2452
 queue_work include/linux/workqueue.h:699 [inline]
 usb_hcd_giveback_urb+0x3b8/0x4a0 drivers/usb/core/hcd.c:1760
 rh_call_control drivers/usb/core/hcd.c:706 [inline]
 rh_urb_enqueue drivers/usb/core/hcd.c:817 [inline]
 usb_hcd_submit_urb+0xab7/0x2150 drivers/usb/core/hcd.c:1538
 usb_submit_urb+0x827/0x19b0 drivers/usb/core/urb.c:586
 usb_start_wait_urb+0x10e/0x580 drivers/usb/core/message.c:62
 usb_internal_control_msg drivers/usb/core/message.c:117 [inline]
 usb_control_msg+0x328/0x4b0 drivers/usb/core/message.c:167
 set_port_feature drivers/usb/core/hub.c:466 [inline]
 hub_suspend+0x826/0x9e0 drivers/usb/core/hub.c:3996
 usb_suspend_interface drivers/usb/core/driver.c:1323 [inline]
 usb_suspend_both+0x288/0x950 drivers/usb/core/driver.c:1446
 usb_runtime_suspend+0x49/0x120 drivers/usb/core/driver.c:2000
 __rpm_callback+0xc8/0x620 drivers/base/power/runtime.c:406
 rpm_callback+0x16a/0x1b0 drivers/base/power/runtime.c:460
 rpm_suspend+0x2f4/0x11a0 drivers/base/power/runtime.c:698
 __pm_runtime_suspend+0xba/0x1a0 drivers/base/power/runtime.c:1167
 pm_runtime_autosuspend include/linux/pm_runtime.h:415 [inline]
 usb_runtime_idle+0x7e/0x90 drivers/usb/core/driver.c:2037
 rpm_idle+0x322/0x790 drivers/base/power/runtime.c:550
 pm_runtime_work+0x120/0x150 drivers/base/power/runtime.c:995
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888026580000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 1272 bytes inside of
 freed 8192-byte region [ffff888026580000, ffff888026582000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26580
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801bc43180 dead000000000122 0000000000000000
raw: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801bc43180 dead000000000122 0000000000000000
head: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 5626878013, free_ts 5419511264
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0xf48/0x3530 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x299/0x2dc0 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3266 [inline]
 allocate_slab mm/slub.c:3380 [inline]
 new_slab+0xa2/0x640 mm/slub.c:3426
 refill_objects+0xe3/0x410 mm/slub.c:7310
 refill_sheaf mm/slub.c:2804 [inline]
 __pcs_replace_empty_main+0x376/0x680 mm/slub.c:4675
 alloc_from_pcs mm/slub.c:4773 [inline]
 slab_alloc_node mm/slub.c:4905 [inline]
 __do_kmalloc_node mm/slub.c:5333 [inline]
 __kvmalloc_node_noprof+0x793/0x970 mm/slub.c:6905
 drm_gem_get_pages+0x146/0x910 drivers/gpu/drm/drm_gem.c:687
 drm_gem_shmem_get_pages_locked+0x1e6/0x4b0 drivers/gpu/drm/drm_gem_shmem_helper.c:242
 drm_gem_shmem_pin_locked+0x224/0x4f0 drivers/gpu/drm/drm_gem_shmem_helper.c:305
 drm_gem_shmem_vmap_locked+0x47f/0x860 drivers/gpu/drm/drm_gem_shmem_helper.c:409
 drm_gem_vmap_locked+0xc8/0x1c0 drivers/gpu/drm/drm_gem.c:1422
 drm_gem_vmap+0x4a/0xa0 drivers/gpu/drm/drm_gem.c:1464
 drm_client_buffer_vmap+0x74/0x110 drivers/gpu/drm/drm_client.c:356
 drm_fbdev_shmem_driver_fbdev_probe+0x344/0xa30 drivers/gpu/drm/drm_fbdev_shmem.c:159
 drm_fb_helper_single_fb_probe drivers/gpu/drm/drm_fb_helper.c:1544 [inline]
 __drm_fb_helper_initial_config_and_unlock+0xe3c/0x17f0 drivers/gpu/drm/drm_fb_helper.c:1725
page last free pid 60 tgid 60 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_pages_prepare+0x586/0xd80 mm/page_alloc.c:1451
 __free_contig_range_common+0x14f/0x250 mm/page_alloc.c:6897
 __free_contig_range mm/page_alloc.c:6942 [inline]
 free_pages_bulk+0x12a/0x200 mm/page_alloc.c:5257
 vm_area_free_pages+0xad/0x2b0 mm/vmalloc.c:3439
 vfree mm/vmalloc.c:3488 [inline]
 vfree+0x107/0x750 mm/vmalloc.c:3462
 delayed_vfree_work+0x56/0x80 mm/vmalloc.c:3392
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff888026580380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888026580400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888026580480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff888026580500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888026580580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
   0:	57                   	push   %rdi
   1:	56                   	push   %rsi
   2:	53                   	push   %rbx
   3:	8b 44 24 14          	mov    0x14(%rsp),%eax
   7:	f6 00 08             	testb  $0x8,(%rax)
   a:	75 23                	jne    0x2f
   c:	8b 44 24 18          	mov    0x18(%rsp),%eax
  10:	8b 5c 24 1c          	mov    0x1c(%rsp),%ebx
  14:	8b 4c 24 20          	mov    0x20(%rsp),%ecx
  18:	8b 54 24 24          	mov    0x24(%rsp),%edx
  1c:	8b 74 24 28          	mov    0x28(%rsp),%esi
  20:	8b 7c 24 2c          	mov    0x2c(%rsp),%edi
  24:	8b 6c 24 30          	mov    0x30(%rsp),%ebp
  28:	cd 80                	int    $0x80
* 2a:	5b                   	pop    %rbx <-- trapping instruction
  2b:	5e                   	pop    %rsi
  2c:	5f                   	pop    %rdi
  2d:	5d                   	pop    %rbp
  2e:	c3                   	ret
  2f:	5b                   	pop    %rbx
  30:	5e                   	pop    %rsi
  31:	5f                   	pop    %rdi
  32:	5d                   	pop    %rbp
  33:	e9 f7 a1 ff ff       	jmp    0xffffa22f
  38:	66 90                	xchg   %ax,%ax
  3a:	66 90                	xchg   %ax,%ax
  3c:	66 90                	xchg   %ax,%ax
  3e:	90                   	nop
  3f:	53                   	push   %rbx

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/02 10:42 upstream 2d2338c93da7 e611ffe1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in attach_store
* Struck through repros no longer work on HEAD.