syzbot

 sign-in | mailing list | source | docs
🐞 Open [818]
🐞 Fixed [85]
🐞 Invalid [1127]
⬇ Missing Backports [132]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

KASAN: use-after-free Read in kernfs_next_descendant_post

Status: auto-obsoleted due to no activity on 2024/01/28 13:25
Reported-by: syzbot+7be0e893a355dad86be9@syzkaller.appspotmail.com
First crash: 772d, last: 772d
▶ ▼ Similar bugs (4)
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 1678d 1674d 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 222d 222d 0/3 auto-obsoleted due to no activity on 2025/07/31 13:17
upstream KASAN: use-after-free Read in kernfs_next_descendant_post (2) usb kernfs 19 C inconclusive error 54 623d 1518d 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 349d 412d 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:1239 [inline]
BUG: KASAN: use-after-free in kernfs_next_descendant_post+0x184/0x200 fs/kernfs/dir.c:1270
Read of size 2 at addr ffff888083c4ec60 by task kworker/0:8/3598

CPU: 0 PID: 3598 Comm: kworker/0:8 Not tainted 5.15.136-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Workqueue: events request_firmware_work_func
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb 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:1239 [inline]
 kernfs_next_descendant_post+0x184/0x200 fs/kernfs/dir.c:1270
 kernfs_activate+0x28/0x200 fs/kernfs/dir.c:1305
 kernfs_add_one+0x4f3/0x640 fs/kernfs/dir.c:776
 kernfs_create_dir_ns+0x1c0/0x230 fs/kernfs/dir.c:1003
 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:2948 [inline]
 get_device_parent+0x391/0x400 drivers/base/core.c:3003
 device_add+0x336/0xfd0 drivers/base/core.c:3315
 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+0xbb1/0x1200 drivers/base/firmware_loader/main.c:848
 request_firmware_work_func+0x126/0x270 drivers/base/firmware_loader/main.c:1097
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
 </TASK>

Allocated by task 3598:
 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:711 [inline]
 __kernfs_new_node+0xdb/0x750 fs/kernfs/dir.c:593
 kernfs_new_node fs/kernfs/dir.c:657 [inline]
 kernfs_create_dir_ns+0x90/0x230 fs/kernfs/dir.c:993
 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:2948 [inline]
 get_device_parent+0x391/0x400 drivers/base/core.c:3003
 device_add+0x336/0xfd0 drivers/base/core.c:3315
 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+0xbb1/0x1200 drivers/base/firmware_loader/main.c:848
 request_firmware_work_func+0x126/0x270 drivers/base/firmware_loader/main.c:1097
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Freed by task 6603:
 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:1381
 kernfs_remove+0x1d/0x30 fs/kernfs/dir.c:1394
 __kobject_del+0xe2/0x310 lib/kobject.c:628
 kobject_del+0x41/0x60 lib/kobject.c:651
 device_del+0x9fe/0xbd0 drivers/base/core.c:3594
 usb_disconnect+0x58f/0x8c0 drivers/usb/core/hub.c:2265
 hub_port_connect drivers/usb/core/hub.c:5281 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5577 [inline]
 port_event drivers/usb/core/hub.c:5723 [inline]
 hub_event+0x1d58/0x54c0 drivers/usb/core/hub.c:5805
 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:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the object at ffff888083c4ebc8
 which belongs to the cache kernfs_node_cache of size 168
The buggy address is located 152 bytes inside of
 168-byte region [ffff888083c4ebc8, ffff888083c4ec70)
The buggy address belongs to the page:
page:ffffea00020f1380 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x83c4e
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 0000000800000001 ffff888011dddb40
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 29530, ts 1218291826976, free_ts 1218290189090
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x322a/0x33c0 mm/page_alloc.c:4159
 __alloc_pages+0x272/0x700 mm/page_alloc.c:5421
 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:711 [inline]
 __kernfs_new_node+0xdb/0x750 fs/kernfs/dir.c:593
 kernfs_new_node+0x95/0x160 fs/kernfs/dir.c:657
 __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
 loop_sysfs_init drivers/block/loop.c:909 [inline]
 loop_configure+0xdd9/0x1470 drivers/block/loop.c:1304
 lo_ioctl+0x933/0x23b0
 blkdev_ioctl+0x333/0x6b0 block/ioctl.c:603
 block_ioctl+0xb1/0xf0 block/fops.c:493
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
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
 tlb_batch_list_free mm/mmu_gather.c:61 [inline]
 tlb_finish_mmu+0x249/0x320 mm/mmu_gather.c:341
 unmap_region+0x304/0x350 mm/mmap.c:2668
 __do_munmap+0x12db/0x1740 mm/mmap.c:2899
 __vm_munmap+0x134/0x230 mm/mmap.c:2922
 __do_sys_munmap mm/mmap.c:2948 [inline]
 __se_sys_munmap mm/mmap.c:2944 [inline]
 __x64_sys_munmap+0x67/0x70 mm/mmap.c:2944
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff888083c4eb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888083c4eb80: fb fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb
>ffff888083c4ec00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
                                                       ^
 ffff888083c4ec80: fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb
 ffff888083c4ed00: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/10/20 13:25 linux-5.15.y 00c03985402e a42250d2 .config console log report info ci2-linux-5-15-kasan KASAN: use-after-free Read in kernfs_next_descendant_post
* Struck through repros no longer work on HEAD.