KASAN: use-after-free Read in kernfs_next_descendant_post (4)

Status: auto-obsoleted due to no activity on 2026/07/25 13:08
Reported-by: syzbot+94c404181b763919a4b6@syzkaller.appspotmail.com
First crash: 112d, last: 112d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in kernfs_next_descendant_post kernfs 19 1 1927d 1923d 0/29 auto-closed as invalid on 2021/08/25 09:05
linux-5.15 KASAN: use-after-free Read in kernfs_next_descendant_post (3) 19 1 471d 471d 0/3 auto-obsoleted due to no activity on 2025/07/31 13:17
linux-5.15 KASAN: use-after-free Read in kernfs_next_descendant_post 19 1 1021d 1021d 0/3 auto-obsoleted due to no activity on 2024/01/28 13:25
upstream KASAN: use-after-free Read in kernfs_next_descendant_post (2) usb kernfs 19 syz, C inconclusive error 54 872d 1767d 0/29 auto-obsoleted due to no activity on 2024/06/25 12:34
linux-5.15 KASAN: use-after-free Read in kernfs_next_descendant_post (2) 19 2 599d 662d 0/3 auto-obsoleted due to no activity on 2025/03/26 02:52

Sample crash report:
usb 1-1: Direct firmware load for ueagle-atm/eagleI.fw failed with error -2
usb 1-1: Falling back to sysfs fallback for: ueagle-atm/eagleI.fw
==================================================================
BUG: KASAN: use-after-free in kernfs_type include/linux/kernfs.h:294 [inline]
BUG: KASAN: use-after-free in kernfs_leftmost_descendant fs/kernfs/dir.c:1251 [inline]
BUG: KASAN: use-after-free in kernfs_next_descendant_post+0x184/0x200 fs/kernfs/dir.c:1282
Read of size 2 at addr ffff888061938520 by task kworker/1:0/21

CPU: 1 PID: 21 Comm: kworker/1:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: events request_firmware_work_func
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 kernfs_type include/linux/kernfs.h:294 [inline]
 kernfs_leftmost_descendant fs/kernfs/dir.c:1251 [inline]
 kernfs_next_descendant_post+0x184/0x200 fs/kernfs/dir.c:1282
 kernfs_activate+0x28/0x210 fs/kernfs/dir.c:1317
 kernfs_add_one+0x55d/0x6c0 fs/kernfs/dir.c:788
 kernfs_create_dir_ns+0xda/0x120 fs/kernfs/dir.c:1015
 sysfs_create_dir_ns+0x12c/0x290 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:89 [inline]
 kobject_add_internal+0x6e0/0xd90 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_add+0x160/0x230 lib/kobject.c:450
 class_dir_create_and_add drivers/base/core.c:2966 [inline]
 get_device_parent+0x380/0x3f0 drivers/base/core.c:3021
 device_add+0x335/0xfb0 drivers/base/core.c:3333
 fw_load_sysfs_fallback drivers/base/firmware_loader/fallback.c:507 [inline]
 fw_load_from_user_helper drivers/base/firmware_loader/fallback.c:583 [inline]
 firmware_fallback_sysfs+0x3e9/0xbc0 drivers/base/firmware_loader/fallback.c:659
 _request_firmware+0xc86/0x12b0 drivers/base/firmware_loader/main.c:876
 request_firmware_work_func+0xac/0x1b0 drivers/base/firmware_loader/main.c:1127
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 21:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 __kasan_slab_alloc+0x9c/0xd0 mm/kasan/common.c:467
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x100/0x290 mm/slub.c:3238
 kmem_cache_zalloc include/linux/slab.h:728 [inline]
 __kernfs_new_node+0xe3/0x6c0 fs/kernfs/dir.c:593
 kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:669
 kernfs_create_dir_ns+0x40/0x120 fs/kernfs/dir.c:1005
 sysfs_create_dir_ns+0x12c/0x290 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:89 [inline]
 kobject_add_internal+0x6e0/0xd90 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_add+0x160/0x230 lib/kobject.c:450
 class_dir_create_and_add drivers/base/core.c:2966 [inline]
 get_device_parent+0x380/0x3f0 drivers/base/core.c:3021
 device_add+0x335/0xfb0 drivers/base/core.c:3333
 fw_load_sysfs_fallback drivers/base/firmware_loader/fallback.c:507 [inline]
 fw_load_from_user_helper drivers/base/firmware_loader/fallback.c:583 [inline]
 firmware_fallback_sysfs+0x3e9/0xbc0 drivers/base/firmware_loader/fallback.c:659
 _request_firmware+0xc86/0x12b0 drivers/base/firmware_loader/main.c:876
 request_firmware_work_func+0xac/0x1b0 drivers/base/firmware_loader/main.c:1127
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 2287:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kmem_cache_free+0x8f/0x210 mm/slub.c:3520
 kernfs_put+0x319/0x490 fs/kernfs/dir.c:547
 __kernfs_remove+0x9d0/0xc70 fs/kernfs/dir.c:1393
 kernfs_remove+0x1d/0x30 fs/kernfs/dir.c:1406
 __kobject_del+0xe1/0x2f0 lib/kobject.c:628
 kobject_del+0x41/0x60 lib/kobject.c:651
 device_del+0x984/0xaf0 drivers/base/core.c:3612
 usb_disconnect+0x573/0x8a0 drivers/usb/core/hub.c:2313
 hub_port_connect drivers/usb/core/hub.c:5341 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5637 [inline]
 port_event drivers/usb/core/hub.c:5799 [inline]
 hub_event+0x1ecb/0x55e0 drivers/usb/core/hub.c:5881
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 process_scheduled_works kernel/workqueue.c:2373 [inline]
 worker_thread+0xd60/0x1290 kernel/workqueue.c:2459
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff888061938488
 which belongs to the cache kernfs_node_cache of size 168
The buggy address is located 152 bytes inside of
 168-byte region [ffff888061938488, ffff888061938530)
The buggy address belongs to the page:
page:ffffea0001864e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x61938
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 dead000000000122 ffff888016de9b40
raw: 0000000000000000 0000000080110011 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 2287, ts 76325693737, free_ts 76279681916
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x80a/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x195/0x290 mm/slub.c:3238
 kmem_cache_zalloc include/linux/slab.h:728 [inline]
 __kernfs_new_node+0xe3/0x6c0 fs/kernfs/dir.c:593
 kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:669
 __kernfs_create_file+0x47/0x2e0 fs/kernfs/file.c:985
 sysfs_add_file_mode_ns+0x2d4/0x3a0 fs/sysfs/file.c:317
 sysfs_merge_group+0x182/0x320 fs/sysfs/group.c:343
 dpm_sysfs_add+0xce/0x270 drivers/base/power/sysfs.c:707
 device_add+0x715/0xfb0 drivers/base/core.c:3369
 usb_create_ep_devs+0x128/0x220 drivers/usb/core/endpoint.c:169
 usb_new_device+0xe86/0x1660 drivers/usb/core/hub.c:2660
 hub_port_connect drivers/usb/core/hub.c:5497 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5637 [inline]
 port_event drivers/usb/core/hub.c:5799 [inline]
 hub_event+0x2e4a/0x55e0 drivers/usb/core/hub.c:5881
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
 free_slab mm/slub.c:2020 [inline]
 discard_slab mm/slub.c:2026 [inline]
 __unfreeze_partials+0x1a5/0x200 mm/slub.c:2512
 put_cpu_partial+0x12d/0x190 mm/slub.c:2592
 qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xd0 mm/kasan/common.c:444
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc_trace+0x103/0x2a0 mm/slub.c:3250
 kmalloc include/linux/slab.h:607 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 device_private_init drivers/base/core.c:3256 [inline]
 device_add+0xba/0xfb0 drivers/base/core.c:3306
 usb_set_configuration+0x1991/0x1fd0 drivers/usb/core/message.c:2165
 usb_generic_driver_probe+0x89/0x150 drivers/usb/core/generic.c:238
 usb_probe_device+0x139/0x270 drivers/usb/core/driver.c:293
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x284/0xc80 drivers/base/dd.c:595
 __driver_probe_device+0x18c/0x330 drivers/base/dd.c:755
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:785

Memory state around the buggy address:
 ffff888061938400: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
 ffff888061938480: fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888061938500: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
                               ^
 ffff888061938580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888061938600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/16 13:07 linux-5.15.y 91d48252ad4b 4743f87d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in kernfs_next_descendant_post
* Struck through repros no longer work on HEAD.