linux-kernel - RE: [PATCH v3 3/4] vsscanf(): do not skip spaces

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Message-ID: <32e8b52d64b642608595142ab2952f16@AcuMS.aculab.com>
Date:   Tue, 13 Jun 2023 12:42:59 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Rasmus Villemoes' <linux@...musvillemoes.dk>,
        Demi Marie Obenour <demi@...isiblethingslab.com>,
        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>,
        "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>
CC:     "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "Christoph Hellwig" <hch@....de>
Subject: RE: [PATCH v3 3/4] vsscanf(): do not skip spaces

From: Rasmus Villemoes
> Sent: 12 June 2023 12:08
> 
> On 10/06/2023 22.40, Demi Marie Obenour wrote:
> > Passing spaces before e.g. an integer is usually
> > not intended.
> 
> Maybe, maybe not. But it's mandated by POSIX/C99.
> 
> And of course we are free to ignore that and implement our own semantics
> (though within the constraints that we really want -Wformat to help us),
> but there seems to be existing code in-tree that relies on this
> behavior. For example I think this will break
> fsl_sata_intr_coalescing_store() which uses a scanf format of "%u%u".
> 
> Sure, that could just say "%u %u" instead, but the point is that
> currently it doesn't. So without some reasonably thorough analysis
> across the tree, and updates of affected callers, NAK.

It would almost certainly need to be " %u %u" to allow for
userspace generating the input with "%6u %6u",

	David

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