[syzbot] KASAN: use-after-free Read in kernfs_next_descendant_post

From: syzbot
Date: Sat May 01 2021 - 05:16:26 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 4a0225c3 Merge tag 'spi-v5.13' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11c0f2b9d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c37352b2923ef305
dashboard link: https://syzkaller.appspot.com/bug?extid=e5d7fe84afc81da312df
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e5d7fe84afc81da312df@xxxxxxxxxxxxxxxxxxxxxxxxx

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:289 [inline]
BUG: KASAN: use-after-free in kernfs_leftmost_descendant fs/kernfs/dir.c:1203 [inline]
BUG: KASAN: use-after-free in kernfs_next_descendant_post+0x1dd/0x290 fs/kernfs/dir.c:1234
Read of size 2 at addr ffff888025e70098 by task kworker/1:6/9747

CPU: 1 PID: 9747 Comm: kworker/1:6 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events request_firmware_work_func
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:233
__kasan_report mm/kasan/report.c:419 [inline]
kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:436
kernfs_type include/linux/kernfs.h:289 [inline]
kernfs_leftmost_descendant fs/kernfs/dir.c:1203 [inline]
kernfs_next_descendant_post+0x1dd/0x290 fs/kernfs/dir.c:1234
kernfs_activate+0x3c/0x1d0 fs/kernfs/dir.c:1269
kernfs_add_one+0x36a/0x4c0 fs/kernfs/dir.c:807
kernfs_create_dir_ns+0x18b/0x220 fs/kernfs/dir.c:1035
sysfs_create_dir_ns+0x127/0x290 fs/sysfs/dir.c:59
create_dir lib/kobject.c:89 [inline]
kobject_add_internal+0x2d2/0xa60 lib/kobject.c:255
kobject_add_varg lib/kobject.c:390 [inline]
kobject_add+0x150/0x1c0 lib/kobject.c:442
class_dir_create_and_add drivers/base/core.c:2871 [inline]
get_device_parent+0x3de/0x590 drivers/base/core.c:2926
device_add+0x2b1/0x2100 drivers/base/core.c:3238
fw_load_sysfs_fallback drivers/base/firmware_loader/fallback.c:509 [inline]
fw_load_from_user_helper drivers/base/firmware_loader/fallback.c:581 [inline]
firmware_fallback_sysfs+0x40b/0xe20 drivers/base/firmware_loader/fallback.c:657
_request_firmware+0xa80/0xe80 drivers/base/firmware_loader/main.c:831
request_firmware_work_func+0xdd/0x230 drivers/base/firmware_loader/main.c:1077
process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 9747:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:427 [inline]
__kasan_slab_alloc+0x75/0x90 mm/kasan/common.c:460
kasan_slab_alloc include/linux/kasan.h:223 [inline]
slab_post_alloc_hook mm/slab.h:516 [inline]
slab_alloc_node mm/slub.c:2907 [inline]
slab_alloc mm/slub.c:2915 [inline]
kmem_cache_alloc+0x153/0x370 mm/slub.c:2920
kmem_cache_zalloc include/linux/slab.h:674 [inline]
__kernfs_new_node+0xd4/0x8b0 fs/kernfs/dir.c:626
kernfs_new_node fs/kernfs/dir.c:688 [inline]
kernfs_create_dir_ns+0x9c/0x220 fs/kernfs/dir.c:1025
sysfs_create_dir_ns+0x127/0x290 fs/sysfs/dir.c:59
create_dir lib/kobject.c:89 [inline]
kobject_add_internal+0x2d2/0xa60 lib/kobject.c:255
kobject_add_varg lib/kobject.c:390 [inline]
kobject_add+0x150/0x1c0 lib/kobject.c:442
class_dir_create_and_add drivers/base/core.c:2871 [inline]
get_device_parent+0x3de/0x590 drivers/base/core.c:2926
device_add+0x2b1/0x2100 drivers/base/core.c:3238
fw_load_sysfs_fallback drivers/base/firmware_loader/fallback.c:509 [inline]
fw_load_from_user_helper drivers/base/firmware_loader/fallback.c:581 [inline]
firmware_fallback_sysfs+0x40b/0xe20 drivers/base/firmware_loader/fallback.c:657
_request_firmware+0xa80/0xe80 drivers/base/firmware_loader/main.c:831
request_firmware_work_func+0xdd/0x230 drivers/base/firmware_loader/main.c:1077
process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Freed by task 9733:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
____kasan_slab_free mm/kasan/common.c:360 [inline]
____kasan_slab_free mm/kasan/common.c:325 [inline]
__kasan_slab_free+0xf5/0x130 mm/kasan/common.c:367
kasan_slab_free include/linux/kasan.h:199 [inline]
slab_free_hook mm/slub.c:1562 [inline]
slab_free_freelist_hook+0x92/0x210 mm/slub.c:1600
slab_free mm/slub.c:3161 [inline]
kmem_cache_free+0x8a/0x730 mm/slub.c:3177
kernfs_put.part.0+0x2c4/0x540 fs/kernfs/dir.c:537
kernfs_put+0x42/0x50 fs/kernfs/dir.c:511
__kernfs_remove+0x703/0xa90 fs/kernfs/dir.c:1345
kernfs_remove+0x1f/0x30 fs/kernfs/dir.c:1358
sysfs_remove_dir+0xc1/0x100 fs/sysfs/dir.c:102
__kobject_del+0xe2/0x200 lib/kobject.c:620
kobject_del lib/kobject.c:643 [inline]
kobject_del+0x3c/0x60 lib/kobject.c:635
device_del+0x816/0xd40 drivers/base/core.c:3519
usb_disconnect.cold+0x4bd/0x791 drivers/usb/core/hub.c:2245
hub_port_connect drivers/usb/core/hub.c:5127 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5416 [inline]
port_event drivers/usb/core/hub.c:5562 [inline]
hub_event+0x1c9c/0x4320 drivers/usb/core/hub.c:5644
process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
process_scheduled_works kernel/workqueue.c:2337 [inline]
worker_thread+0x82b/0x1120 kernel/workqueue.c:2423
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the object at ffff888025e70000
which belongs to the cache kernfs_node_cache of size 168
The buggy address is located 152 bytes inside of
168-byte region [ffff888025e70000, ffff888025e700a8)
The buggy address belongs to the page:
page:ffffea0000979c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x25e70
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 ffffea0000a78000 0000000500000005 ffff8880111bd780
raw: 0000000000000000 0000000080110011 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888025e6ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888025e70000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888025e70080: fb fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb
^
ffff888025e70100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888025e70180: fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb fb
==================================================================

---
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Next message: Phillip Potter: "Re: [PATCH] fs: ext4: mballoc: amend goto to cleanup groupinfo memory correctly"
Previous message: Ywe Cærlyn: "Fair Pay: Regular latin (christian) not fair pay compliant, use Cursive."
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