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SubjectKASAN: use-after-free Read in kobject_put
From
Hello,

syzbot found the following crash on:

HEAD commit: fa520c47eaa1 fscache: Fix out of bound read in long cookie..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15f664f6400000
kernel config: https://syzkaller.appspot.com/x/.config?x=b3f55cb3dfcc6c33
dashboard link: https://syzkaller.appspot.com/bug?extid=fdc00003f4efff43bc5b
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fdc00003f4efff43bc5b@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in kobject_put+0xcb/0xe0 lib/kobject.c:704
Read of size 1 at addr ffff88018515a3cc by task syz-executor4/11682

CPU: 1 PID: 11682 Comm: syz-executor4 Not tainted 4.19.0-rc8+ #290
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
__asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
kobject_put+0xcb/0xe0 lib/kobject.c:704
put_device+0x20/0x30 drivers/base/core.c:2024
hci_free_dev+0x19/0x20 net/bluetooth/hci_core.c:3143
vhci_release+0x7e/0xf0 drivers/bluetooth/hci_vhci.c:355
__fput+0x385/0xa30 fs/file_table.c:278
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x411021
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 34 19 00 00 c3 48
83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48
89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffc03715460 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000411021
RDX: 0000000000000000 RSI: 0000000000730348 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000730338 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000001 R14: 000000000000003c R15: 0000000000000004

Allocated by task 11686:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:513 [inline]
kzalloc include/linux/slab.h:707 [inline]
hci_alloc_dev+0x228/0x2120 net/bluetooth/hci_core.c:3053
__vhci_create_device+0x102/0x580 drivers/bluetooth/hci_vhci.c:114
vhci_create_device drivers/bluetooth/hci_vhci.c:163 [inline]
vhci_get_user drivers/bluetooth/hci_vhci.c:219 [inline]
vhci_write+0x2de/0x470 drivers/bluetooth/hci_vhci.c:299
call_write_iter include/linux/fs.h:1808 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x6b8/0x9f0 fs/read_write.c:487
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 11682:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3813
bt_host_release+0x19/0x30 net/bluetooth/hci_sysfs.c:86
device_release+0x7e/0x210 drivers/base/core.c:891
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold.9+0x287/0x2e4 lib/kobject.c:708
put_device+0x20/0x30 drivers/base/core.c:2024
hci_dev_put include/net/bluetooth/hci_core.h:1004 [inline]
hci_unregister_dev+0x71d/0x990 net/bluetooth/hci_core.c:3314
vhci_release+0x76/0xf0 drivers/bluetooth/hci_vhci.c:354
__fput+0x385/0xa30 fs/file_table.c:278
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff880185159300
which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 4300 bytes inside of
8192-byte region [ffff880185159300, ffff88018515b300)
The buggy address belongs to the page:
page:ffffea0006145600 count:1 mapcount:0 mapping:ffff8801da802080 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffffea0006211e08 ffffea0006156408 ffff8801da802080
raw: 0000000000000000 ffff880185159300 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88018515a280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88018515a300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88018515a380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88018515a400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88018515a480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
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