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SubjectKASAN: use-after-free Write in as102_release
From
Hello,

syzbot found the following crash on:

HEAD commit: 32b5e2b2 usb: gadget: add raw-gadget interface
git tree: https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=1255457ae00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d88612251f7691bd
dashboard link: https://syzkaller.appspot.com/bug?extid=edff65c4ade21b5db190
compiler: gcc (GCC) 9.0.0 20181231 (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+edff65c4ade21b5db190@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in atomic_fetch_sub
include/asm-generic/atomic-instrumented.h:199 [inline]
BUG: KASAN: use-after-free in refcount_sub_and_test
include/linux/refcount.h:253 [inline]
BUG: KASAN: use-after-free in refcount_dec_and_test
include/linux/refcount.h:281 [inline]
BUG: KASAN: use-after-free in kref_put include/linux/kref.h:64 [inline]
BUG: KASAN: use-after-free in as102_release+0x58/0xd8
drivers/media/usb/as102/as102_usb_drv.c:458
Write of size 4 at addr ffff8881adb84140 by task syz-executor.5/16315

CPU: 1 PID: 16315 Comm: syz-executor.5 Not tainted 5.4.0-syzkaller #0
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+0xef/0x16e lib/dump_stack.c:118
print_address_description.constprop.0+0x36/0x50 mm/kasan/report.c:374
__kasan_report.cold+0x1a/0x33 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:634
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x128/0x190 mm/kasan/generic.c:192
atomic_fetch_sub include/asm-generic/atomic-instrumented.h:199 [inline]
refcount_sub_and_test include/linux/refcount.h:253 [inline]
refcount_dec_and_test include/linux/refcount.h:281 [inline]
kref_put include/linux/kref.h:64 [inline]
as102_release+0x58/0xd8 drivers/media/usb/as102/as102_usb_drv.c:458
__fput+0x2d7/0x840 fs/file_table.c:280
task_work_run+0x13f/0x1c0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x8ab/0x2bc0 kernel/exit.c:797
do_group_exit+0x125/0x340 kernel/exit.c:895
get_signal+0x466/0x23c0 kernel/signal.c:2734
do_signal+0x88/0x1490 arch/x86/kernel/signal.c:815
exit_to_usermode_loop+0x1a2/0x200 arch/x86/entry/common.c:160
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
do_syscall_64+0x4d1/0x5b0 arch/x86/entry/common.c:304
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a4e7
Code: Bad RIP value.
RSP: 002b:00007f8274f103c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: fffffffffffffffc RBX: 0000000000000000 RCX: 000000000045a4e7
RDX: 00007f8274f10810 RSI: 0000000080085502 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00000000004ca701 R14: 00000000004e2e78 R15: 00000000ffffffff

Allocated by task 17:
save_stack+0x1b/0x80 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_kmalloc mm/kasan/common.c:510 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:483
kmalloc include/linux/slab.h:556 [inline]
kzalloc include/linux/slab.h:690 [inline]
as102_usb_probe+0x4e/0x3d0 drivers/media/usb/as102/as102_usb_drv.c:350
usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x104/0x210 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
device_add+0x1480/0x1c20 drivers/base/core.c:2487
usb_set_configuration+0xe67/0x1740 drivers/usb/core/message.c:2023
generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x104/0x210 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
device_add+0x1480/0x1c20 drivers/base/core.c:2487
usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2537
hub_port_connect drivers/usb/core/hub.c:5184 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5324 [inline]
port_event drivers/usb/core/hub.c:5470 [inline]
hub_event+0x1e59/0x3860 drivers/usb/core/hub.c:5552
process_one_work+0x92b/0x1530 kernel/workqueue.c:2264
worker_thread+0x96/0xe20 kernel/workqueue.c:2410
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Freed by task 17:
save_stack+0x1b/0x80 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
kasan_set_free_info mm/kasan/common.c:332 [inline]
__kasan_slab_free+0x130/0x180 mm/kasan/common.c:471
slab_free_hook mm/slub.c:1424 [inline]
slab_free_freelist_hook mm/slub.c:1457 [inline]
slab_free mm/slub.c:3004 [inline]
kfree+0xdc/0x310 mm/slub.c:3956
as102_usb_probe.cold+0x133/0x366
drivers/media/usb/as102/as102_usb_drv.c:412
usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x104/0x210 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
device_add+0x1480/0x1c20 drivers/base/core.c:2487
usb_set_configuration+0xe67/0x1740 drivers/usb/core/message.c:2023
generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x104/0x210 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
device_add+0x1480/0x1c20 drivers/base/core.c:2487
usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2537
hub_port_connect drivers/usb/core/hub.c:5184 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5324 [inline]
port_event drivers/usb/core/hub.c:5470 [inline]
hub_event+0x1e59/0x3860 drivers/usb/core/hub.c:5552
process_one_work+0x92b/0x1530 kernel/workqueue.c:2264
worker_thread+0x96/0xe20 kernel/workqueue.c:2410
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8881adb84000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 320 bytes inside of
4096-byte region [ffff8881adb84000, ffff8881adb85000)
The buggy address belongs to the page:
page:ffffea0006b6e000 refcount:1 mapcount:0 mapping:ffff8881da00c280
index:0x0 compound_mapcount: 0
raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881da00c280
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881adb84000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881adb84080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881adb84100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881adb84180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881adb84200: 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.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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