From: Oliver Neukum <oneukum@suse.com>
To: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Alan Stern <stern@rowland.harvard.edu>,
LKML <linux-kernel@vger.kernel.org>,
linux-usb@vger.kernel.org,
Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Subject: Re: UBSAN whinge in ihci-hub.c
Date: Wed, 18 May 2016 10:18:27 +0200 [thread overview]
Message-ID: <1463559507.22748.12.camel@suse.com> (raw)
In-Reply-To: <CAPAsAGxMnbpzuDGLOLr48qqJyU9GGC1_2TAOr9oA_F7jaupk3w@mail.gmail.com>
On Wed, 2016-05-18 at 10:40 +0300, Andrey Ryabinin wrote:
> 2016-05-18 1:16 GMT+03:00 Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
> > On Tue, May 17, 2016 at 05:52:40PM -0400, Valdis Kletnieks wrote:
> >> So, not content in the amount of breakage I generate already, I
> >> compiled with UBSAN enabled...
> >>
> >> The immediately relevant part:
> >>
> >> [ 2.418576] ================================================================================
> >> [ 2.418579] UBSAN: Undefined behaviour in drivers/usb/host/ehci-hub.c:877:47
> >> [ 2.418582] index -1 is out of range for type 'u32 [1]'
> >
> > <snip>
> >
> > It's a known bug in ubsan,
>
> It's not a bug. int *p = &a[-1] is undefined behavior. It doesn't
> matter whether that pointer dereferenced or not.
That is a bold statement. Pointer arithmetic is defined. How can
the computation of an address be undefined behavior while it is
not used?
Regards
Oliver
next prev parent reply other threads:[~2016-05-18 8:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-17 21:52 UBSAN whinge in ihci-hub.c Valdis Kletnieks
2016-05-17 22:16 ` Greg Kroah-Hartman
2016-05-18 7:40 ` Andrey Ryabinin
2016-05-18 8:18 ` Oliver Neukum [this message]
2016-05-18 9:16 ` Andrey Ryabinin
2016-05-18 10:19 ` Oliver Neukum
2016-05-18 12:21 ` Andrey Ryabinin
2016-05-18 14:40 ` Alan Stern
2016-05-18 15:02 ` Andrey Ryabinin
2016-05-18 16:09 ` Alan Stern
2016-05-18 17:15 ` Andrey Ryabinin
2016-05-18 19:28 ` Alan Stern
2016-05-19 16:29 ` Andrey Ryabinin
2016-05-19 20:11 ` Alan Stern
2016-05-23 15:58 ` David Laight
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