KASAN: use-after-free Read in kernfs_next_descendant_post (3)

Status: auto-obsoleted due to no activity on 2025/07/31 13:17
Reported-by: syzbot+b3f32cb52f2a9e45b492@syzkaller.appspotmail.com
First crash: 472d, last: 472d
▶ ▼ 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 1928d 1924d 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 (4) 19 1 113d 113d 0/3 auto-obsoleted due to no activity on 2026/07/25 13:08
linux-5.15 KASAN: use-after-free Read in kernfs_next_descendant_post 19 1 1022d 1022d 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 873d 1768d 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 4-1: Direct firmware load for ueagle-atm/eagleI.fw failed with error -2
usb 4-1: 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 ffff88805b32b098 by task kworker/0:6/4222

CPU: 0 PID: 4222 Comm: kworker/0:6 Not tainted 5.15.180-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: events request_firmware_work_func
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 print_address_description+0x63/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0x16b/0x1c0 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+0x28/0x200 fs/kernfs/dir.c:1317
 kernfs_add_one+0x4f3/0x640 fs/kernfs/dir.c:788
 kernfs_create_dir_ns+0xd5/0x120 fs/kernfs/dir.c:1015
 sysfs_create_dir_ns+0x185/0x390 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:89 [inline]
 kobject_add_internal+0x6e0/0xe00 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_add+0x14e/0x210 lib/kobject.c:450
 class_dir_create_and_add drivers/base/core.c:2966 [inline]
 get_device_parent+0x391/0x400 drivers/base/core.c:3021
 device_add+0x336/0xfd0 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+0x3f0/0xc90 drivers/base/firmware_loader/fallback.c:659
 _request_firmware+0xc72/0x12c0 drivers/base/firmware_loader/main.c:876
 request_firmware_work_func+0x126/0x270 drivers/base/firmware_loader/main.c:1127
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 4222:
 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+0x8e/0xc0 mm/kasan/common.c:467
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x53/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3220 [inline]
 slab_alloc mm/slub.c:3228 [inline]
 kmem_cache_alloc+0xf3/0x280 mm/slub.c:3233
 kmem_cache_zalloc include/linux/slab.h:725 [inline]
 __kernfs_new_node+0xdb/0x750 fs/kernfs/dir.c:593
 kernfs_new_node+0x136/0x230 fs/kernfs/dir.c:669
 kernfs_create_dir_ns+0x3f/0x120 fs/kernfs/dir.c:1005
 sysfs_create_dir_ns+0x185/0x390 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:89 [inline]
 kobject_add_internal+0x6e0/0xe00 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_add+0x14e/0x210 lib/kobject.c:450
 class_dir_create_and_add drivers/base/core.c:2966 [inline]
 get_device_parent+0x391/0x400 drivers/base/core.c:3021
 device_add+0x336/0xfd0 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+0x3f0/0xc90 drivers/base/firmware_loader/fallback.c:659
 _request_firmware+0xc72/0x12c0 drivers/base/firmware_loader/main.c:876
 request_firmware_work_func+0x126/0x270 drivers/base/firmware_loader/main.c:1127
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 5779:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x80 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd8/0x120 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1705 [inline]
 slab_free_freelist_hook+0xdd/0x160 mm/slub.c:1731
 slab_free mm/slub.c:3499 [inline]
 kmem_cache_free+0x91/0x1f0 mm/slub.c:3515
 kernfs_put+0x325/0x4a0 fs/kernfs/dir.c:547
 __kernfs_remove+0x99e/0xc80 fs/kernfs/dir.c:1393
 kernfs_remove+0x1d/0x30 fs/kernfs/dir.c:1406
 __kobject_del+0xe2/0x310 lib/kobject.c:628
 kobject_del+0x41/0x60 lib/kobject.c:651
 device_del+0x9fe/0xbd0 drivers/base/core.c:3612
 usb_disconnect+0x58f/0x8c0 drivers/usb/core/hub.c:2285
 hub_port_connect drivers/usb/core/hub.c:5311 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5607 [inline]
 port_event drivers/usb/core/hub.c:5753 [inline]
 hub_event+0x1d58/0x54c0 drivers/usb/core/hub.c:5835
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 process_scheduled_works kernel/workqueue.c:2373 [inline]
 worker_thread+0xdcf/0x1280 kernel/workqueue.c:2459
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff88805b32b000
 which belongs to the cache kernfs_node_cache of size 168
The buggy address is located 152 bytes inside of
 168-byte region [ffff88805b32b000, ffff88805b32b0a8)
The buggy address belongs to the page:
page:ffffea00016ccac0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5b32b
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 0000000a00000001 ffff8880175eab40
raw: 0000000000000000 0000000000110011 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 5897, ts 191745008918, free_ts 190337274672
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x3b78/0x3d40 mm/page_alloc.c:4192
 __alloc_pages+0x272/0x700 mm/page_alloc.c:5466
 alloc_slab_page mm/slub.c:1775 [inline]
 allocate_slab mm/slub.c:1912 [inline]
 new_slab+0xbb/0x4b0 mm/slub.c:1975
 ___slab_alloc+0x6f6/0xe10 mm/slub.c:3008
 __slab_alloc mm/slub.c:3095 [inline]
 slab_alloc_node mm/slub.c:3186 [inline]
 slab_alloc mm/slub.c:3228 [inline]
 kmem_cache_alloc+0x18e/0x280 mm/slub.c:3233
 kmem_cache_zalloc include/linux/slab.h:725 [inline]
 __kernfs_new_node+0xdb/0x750 fs/kernfs/dir.c:593
 kernfs_new_node+0x136/0x230 fs/kernfs/dir.c:669
 __kernfs_create_file+0x45/0x2e0 fs/kernfs/file.c:985
 sysfs_add_file_mode_ns+0x308/0x3e0 fs/sysfs/file.c:317
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x573/0xf00 fs/sysfs/group.c:149
 internal_create_groups fs/sysfs/group.c:189 [inline]
 sysfs_create_groups+0x52/0x110 fs/sysfs/group.c:215
 create_dir lib/kobject.c:100 [inline]
 kobject_add_internal+0x83b/0xe00 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_init_and_add+0x120/0x190 lib/kobject.c:481
 ext4_register_sysfs+0xb2/0x2b0 fs/ext4/sysfs.c:529
 ext4_fill_super+0x942e/0xa110 fs/ext4/super.c:4950
 mount_bdev+0x2c9/0x3f0 fs/super.c:1400
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+0xc34/0xcf0 mm/page_alloc.c:3317
 free_unref_page+0x95/0x2d0 mm/page_alloc.c:3396
 kasan_depopulate_vmalloc_pte+0x66/0x80 mm/kasan/shadow.c:375
 apply_to_pte_range mm/memory.c:2573 [inline]
 apply_to_pmd_range mm/memory.c:2617 [inline]
 apply_to_pud_range mm/memory.c:2653 [inline]
 apply_to_p4d_range mm/memory.c:2689 [inline]
 __apply_to_page_range+0x9bf/0xcc0 mm/memory.c:2725
 kasan_release_vmalloc+0x96/0xb0 mm/kasan/shadow.c:485
 __purge_vmap_area_lazy+0x15ae/0x1740 mm/vmalloc.c:1704
 _vm_unmap_aliases+0x453/0x4e0 mm/vmalloc.c:2107
 vm_remove_mappings mm/vmalloc.c:2584 [inline]
 __vunmap+0x71b/0xa50 mm/vmalloc.c:2611
 bpf_jit_binary_free kernel/bpf/core.c:918 [inline]
 bpf_jit_free+0x92/0x180 kernel/bpf/core.c:931
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Memory state around the buggy address:
 ffff88805b32af80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88805b32b000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805b32b080: fb fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb
                            ^
 ffff88805b32b100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805b32b180: fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/04/22 13:17 linux-5.15.y f7347f400572 2a20f901 .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.