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Date:   Thu, 8 Aug 2019 14:46:54 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     syzbot <syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com>,
        Michael Hund <mhund@ld-didactic.de>
Cc:     akpm@linux-foundation.org, andreyknvl@google.com, cai@lca.pw,
        keescook@chromium.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-usb@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, tglx@linutronix.de
Subject: Re: BUG: bad usercopy in ld_usb_read
Message-ID: <20190808124654.GB32144@kroah.com>
References: <0000000000005c056c058f9a5437@google.com>
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On Thu, Aug 08, 2019 at 05:38:06AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=13aeaece600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
> 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+45b2f40f0778cfa7634e@syzkaller.appspotmail.com
> 
> ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped

That's a funny number :)

Nice overflow found, I see you are now starting to fuzz the char device
nodes of usb drivers...

Michael, care to fix this up?

thanks,

greg k-h