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Message-ID: <ZIoeVjC6offUywop@itl-email>
Date: Wed, 14 Jun 2023 16:08:51 -0400
From: Demi Marie Obenour <demi@...isiblethingslab.com>
To: David Laight <David.Laight@...lab.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Hans de Goede <hdegoede@...hat.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Sakari Ailus <sakari.ailus@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Juergen Gross <jgross@...e.com>,
Stefano Stabellini <sstabellini@...nel.org>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
Lee Jones <lee@...nel.org>, Andy Lutomirski <luto@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH v3 0/4] Make sscanf() stricter
On Wed, Jun 14, 2023 at 08:23:56AM +0000, David Laight wrote:
> From: Demi Marie Obenour
> > Sent: 13 June 2023 16:35
> >
> > On Tue, Jun 13, 2023 at 01:02:59PM +0000, David Laight wrote:
> > > From: Demi Marie Obenour
> > > > Sent: 12 June 2023 22:23
> > > ....
> > > > sscanf(), except to the extent that -Werror=format can keep working.
> > > > Userspace sscanf() is almost useless: it has undefined behavior on
> > > > integer overflow and swallows spaces that should usually be rejected.
> > >
> > > scanf() is designed for parsing space separated data.
> > > Eating spaces it part of its job description.
> > >
> > > David
> >
> > In this case I would prefer to have two versions: one that eats spaces
> > and one that does not. For instance, I don’t think any user of
> > xenbus_scanf() wants the space-swallowing behavior. This can be worked
> > around in xenbus_scanf(), of course, by having it reject strings with
> > spaces (as determened by isspace()) before calling vsscanf().
>
> What sort of formats and data are being used?
Base-10 or base-16 integers, with whitespace never being valid.
> The "%s" format terminates on whitespace.
> Even stroul() (and friends) will skip leading whitespace.
Yes, which is a reason that strto*l() are just broken IMO. I’m trying
to replace their uses in Xen with custom parsing code.
--
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
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