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Message-ID: <d17aef8a-adbe-9d90-3173-60eb2f0828a5@gmail.com>
Date:   Sat, 12 Mar 2022 18:08:18 +0300
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Subject: Re: [syzbot] memory leak in usb_get_configuration
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To:     Alan Stern <stern@rowland.harvard.edu>,
        syzbot <syzbot+f0fae482604e6d9a87c9@syzkaller.appspotmail.com>
Cc:     gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org, pavel.hofman@ivitera.com,
        rob@robgreener.com, syzkaller-bugs@googlegroups.com
References: <000000000000351b8605d9d1d1bf@google.com>
 <Yiu4tCONfHVH1Qfv@rowland.harvard.edu>
From:   Pavel Skripkin <paskripkin@gmail.com>
In-Reply-To: <Yiu4tCONfHVH1Qfv@rowland.harvard.edu>
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Hi Alan,

On 3/12/22 00:01, Alan Stern wrote:
> On Wed, Mar 09, 2022 at 03:54:24PM -0800, syzbot wrote:
>> Hello,
>> 
>> syzbot found the following issue on:
>> 
>> HEAD commit:    0014404f9c18 Merge branch 'akpm' (patches from Andrew)
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=15864216700000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=3f0a704147ec8e32
>> dashboard link: https://syzkaller.appspot.com/bug?extid=f0fae482604e6d9a87c9
>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13a63dbe700000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10e150a1700000
>> 
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+f0fae482604e6d9a87c9@syzkaller.appspotmail.com
>> 
>> BUG: memory leak
>> unreferenced object 0xffff88810c0289e0 (size 32):
>>   comm "kworker/1:2", pid 139, jiffies 4294947862 (age 15.910s)
>>   hex dump (first 32 bytes):
>>     09 02 12 00 01 00 00 00 00 09 04 00 00 00 d0 bb  ................
>>     3a 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :...............
>>   backtrace:
>>     [<ffffffff82c98127>] kmalloc include/linux/slab.h:586 [inline]
>>     [<ffffffff82c98127>] usb_get_configuration+0x1c7/0x1cd0 drivers/usb/core/config.c:919
>>     [<ffffffff82c863f9>] usb_enumerate_device drivers/usb/core/hub.c:2398 [inline]
>>     [<ffffffff82c863f9>] usb_new_device+0x1a9/0x2e0 drivers/usb/core/hub.c:2536
>>     [<ffffffff82c88ea4>] hub_port_connect drivers/usb/core/hub.c:5358 [inline]
>>     [<ffffffff82c88ea4>] hub_port_connect_change drivers/usb/core/hub.c:5502 [inline]
>>     [<ffffffff82c88ea4>] port_event drivers/usb/core/hub.c:5660 [inline]
>>     [<ffffffff82c88ea4>] hub_event+0x1364/0x21a0 drivers/usb/core/hub.c:5742
>>     [<ffffffff8126a41f>] process_one_work+0x2bf/0x600 kernel/workqueue.c:2307
>>     [<ffffffff8126ad49>] worker_thread+0x59/0x5b0 kernel/workqueue.c:2454
>>     [<ffffffff81274705>] kthread+0x125/0x160 kernel/kthread.c:377
>>     [<ffffffff810021ef>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> 
> The console log shows that this is connected to gspca_dev_probe.  Let's
> see who's calling it...
> 

The execution path is more complicated. I've done some debugging, but no 
luck with root case... Just want to share what I found and maybe it will 
help.

Firsly syzbot connects carl9170 device (usb ids from the log). 
carl9170_usb_probe() calls usb_reset_device() which fails with -19. If I 
remove this usb_reset_device() call then issue is no more reproducible.

Then 2 other probes are called: usbtest and spca501. spca501 calls 
gspca_dev_probe(), but it fails early and I do not suspect this driver.
usbtest probe function also looks correct, so I do not suspect this 
driver as well.

Looks like the issue either in usb_reset_device() call or somewhere in 
usb internals


With regards,
Pavel Skripkin