linux-kernel - Re: [PATCH v6 9/9] vsprintf: Avoid confusion between invalid address and value

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Message-ID: <20190214084256.c26jd2b7oow3eatt@pathway.suse.cz>
Date:   Thu, 14 Feb 2019 09:42:56 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Tobin C . Harding" <me@...in.cc>, Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 9/9] vsprintf: Avoid confusion between invalid address
 and value

On Wed 2019-02-13 15:54:55, Andy Shevchenko wrote:
> On Tue, Feb 12, 2019 at 04:45:30PM +0100, Petr Mladek wrote:
> > On Fri 2019-02-08 19:27:17, Andy Shevchenko wrote:
> > > On Fri, Feb 08, 2019 at 04:23:10PM +0100, Petr Mladek wrote:
> > > > We are able to detect invalid values handled by %p[iI] printk specifier.
> > > > The current error message is "invalid address". It might cause confusion
> > > > against "(efault)" reported by the generic valid_pointer_address() check.
> > > > 
> > > > Let's unify the style and use the more appropriate error code description
> > > > "(einval)".
> > > 
> > > The proper one should be "invalid address family". The proposed change
> > > increases confusion.
> > 
> > I am confused. Is there any error code for "invalid address family"?
> 
> I'm not sure.
> There is EAFNOSUPPORT. I don't know if it suits better.

I would not complicate it. EAFNOSUPPORT looks too special,
see below. Also it is controversial here because vsprintf()
does not implement any protocol.


> > EINVAL is standard error code used when a wrong value is passed
> > as a parameter. In this case, the code is not able to handle
> > the given address family.
> 
> This is possible, but it will produce more generic message.

I am not sure that I understand it. We do not pass the error code
anywhere. The patch only changes the string that is shown instead
of the requested value. It is a hint that something is wrong
either with the caller or with the vsprintf() implementation.

I think that it does not make sense to do a big deal from it.
"(einval)" looks informative enough to me.

Best Regards,
Petr