From: Kees Cook <keescook@chromium.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg KH <gregkh@linuxfoundation.org>,
syzbot <syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com>,
Michael Hund <mhund@ld-didactic.de>,
akpm@linux-foundation.org, andreyknvl@google.com, cai@lca.pw,
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
Date: Sat, 10 Aug 2019 11:23:18 -0700 [thread overview]
Message-ID: <201908101120.BE5034521A@keescook> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1908091100580.1630-100000@iolanthe.rowland.org>
On Fri, Aug 09, 2019 at 11:13:00AM -0400, Alan Stern wrote:
> In fact, I don't see why any of the computations here should overflow
> or wrap around, or even give rise to a negative value. If syzbot had a
> reproducer we could get more debugging output -- but it doesn't.
Yeah, this is odd. The only thing I could see here with more study was
that ring_tail is used/updated outside of the rbsl lock in
ld_usb_read(). I couldn't convince myself there wasn't a race against
the interrupt, but I also couldn't think of a way it could break...
--
Kees Cook
next prev parent reply other threads:[~2019-08-10 18:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-08 12:38 BUG: bad usercopy in ld_usb_read syzbot
2019-08-08 12:46 ` Greg KH
2019-08-08 23:06 ` Kees Cook
2019-08-09 8:55 ` Greg KH
2019-08-09 15:13 ` Alan Stern
2019-08-10 18:23 ` Kees Cook [this message]
2019-08-10 18:15 ` syzbot
2019-08-12 12:06 ` Andrey Konovalov
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