Re: KMSAN: uninit-value in adu_disconnect

[Johan Hovold]

On Mon, Sep 30, 2019 at 08:29:07PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    014077b5 DO-NOT-SUBMIT: usb-fuzzer: main usb gadget fuzzer..
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=108b5826600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f03c659d0830ab8d
> dashboard link: https://syzkaller.appspot.com/bug?extid=224d4aba0201decca39c
> compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
> 80fee25776c2fb61e74c1ecb1a523375c2500b69)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15abd5c1600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=168e3a3a600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+224d4aba0201decca39c@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> usb 1-1: USB disconnect, device number 23
> ==================================================================
> BUG: KMSAN: uninit-value in adu_disconnect+0x302/0x360  
> drivers/usb/misc/adutux.c:774
> CPU: 0 PID: 3372 Comm: kworker/0:2 Not tainted 5.3.0-rc7+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x191/0x1f0 lib/dump_stack.c:113
>   kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
>   __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
>   adu_disconnect+0x302/0x360 drivers/usb/misc/adutux.c:774
>   usb_unbind_interface+0x3a2/0xdd0 drivers/usb/core/driver.c:423
>   __device_release_driver drivers/base/dd.c:1120 [inline]
>   device_release_driver_internal+0x911/0xd20 drivers/base/dd.c:1151
>   device_release_driver+0x4b/0x60 drivers/base/dd.c:1174
>   bus_remove_device+0x4bf/0x670 drivers/base/bus.c:556
>   device_del+0xcd5/0x1d10 drivers/base/core.c:2339
>   usb_disable_device+0x567/0x1150 drivers/usb/core/message.c:1241
>   usb_disconnect+0x51e/0xd60 drivers/usb/core/hub.c:2199
>   hub_port_connect drivers/usb/core/hub.c:4949 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
>   port_event drivers/usb/core/hub.c:5359 [inline]
>   hub_event+0x3fd0/0x72f0 drivers/usb/core/hub.c:5441
>   process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
>   worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
>   kthread+0x4b5/0x4f0 kernel/kthread.c:256
>   ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
> 
> Uninit was created at:
>   kmsan_save_stack_with_flags mm/kmsan/kmsan.c:189 [inline]
>   kmsan_internal_poison_shadow+0x58/0xb0 mm/kmsan/kmsan.c:148
>   kmsan_slab_free+0x8d/0x100 mm/kmsan/kmsan_hooks.c:195
>   slab_free_freelist_hook mm/slub.c:1472 [inline]
>   slab_free mm/slub.c:3038 [inline]
>   kfree+0x4c1/0x2db0 mm/slub.c:3980
>   adu_delete drivers/usb/misc/adutux.c:151 [inline]
>   adu_release+0x95f/0xa50 drivers/usb/misc/adutux.c:332
>   __fput+0x4c9/0xba0 fs/file_table.c:280
>   ____fput+0x37/0x40 fs/file_table.c:313
>   task_work_run+0x22e/0x2a0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop arch/x86/entry/common.c:163 [inline]
>   prepare_exit_to_usermode+0x39d/0x4d0 arch/x86/entry/common.c:194
>   syscall_return_slowpath+0x90/0x610 arch/x86/entry/common.c:274
>   do_syscall_64+0xe2/0xf0 arch/x86/entry/common.c:300
>   entry_SYSCALL_64_after_hwframe+0x63/0xe7
> ==================================================================

Likely another manifestation of

#sys dup: KASAN: use-after-free Read in adu_disconnect

Fix posted here

	https://lkml.kernel.org/r/20190925092913.8608-1-johan@xxxxxxxxxx

Johan