Re: [PATCH] usb: mon: Fix a deadlock in usbmon between mmap and read

From: Greg KH <greg@kroah.com>
To: Pete Zaitcev <zaitcev@redhat.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
	USB list <linux-usb@vger.kernel.org>
Subject: Re: [PATCH] usb: mon: Fix a deadlock in usbmon between mmap and read
Date: Wed, 27 Nov 2019 07:55:19 +0100	[thread overview]
Message-ID: <20191127065519.GA1724976@kroah.com> (raw)
In-Reply-To: <20191126223509.69fb61ed@suzdal.zaitcev.lan>

On Tue, Nov 26, 2019 at 10:35:09PM -0600, Pete Zaitcev wrote:
> On Tue, 26 Nov 2019 10:20:14 -0500 (EST)
> Alan Stern <stern@rowland.harvard.edu> wrote:
> 
> > > Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
> > > Reported-by: syzbot+56f9673bb4cdcbeb0e92@syzkaller.appspotmail.com  
> > 
> > Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
> 
> Thanks.
> 
> > Fixes: 46eb14a6e158 ("USB: fix usbmon BUG trigger")
> 
> Indeed... Either I didn't think that one through, or the copy_to_user
> used not to take the mmap_sem.
> 
> > CC: <stable@vger.kernel.org>
> 
> Do we really need this? The problem was in the code for more than 10 years.
> It's not like anyone is exploiting systems because of it.

Well now we all have a simple reproducer for it, so yes, it should be
backported.  I'm doing that for all of the syzbot stuff.

> If we do need it, I should cc: the submission to the same place too, right?

Nope, the tag is just fine, that's all that is needed.  I'll add the
above to the patch when applying it to my trees.

thanks,

greg k-h