linux-kernel - Re: [PATCH] vsprintf: don't obfuscate NULL and error pointers

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Date:   Tue, 18 Feb 2020 20:31:36 +0100
From:   Adam Borowski <kilobyte@...band.pl>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Ilya Dryomov <idryomov@...il.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        "Tobin C . Harding" <me@...in.cc>
Subject: Re: [PATCH] vsprintf: don't obfuscate NULL and error pointers

On Tue, Feb 18, 2020 at 10:49:30AM -0800, Linus Torvalds wrote:
> On Mon, Feb 17, 2020 at 4:07 PM Ilya Dryomov <idryomov@...il.com> wrote:
> >
> > I'm not sure what you mean by efault string.  Are you referring to what
> > %pe is doing?  If so, no -- I would keep %p and %pe separate.
> 
> Right.
> 
> But bringing up %pe makes me realize that we do odd things for NULL
> for that. We print errors in a nice legible form, but we show NULL as
> a zero value, I think.
> 
> So maybe %pe should show NULL as "(null)"? Or even as just "0" to go
> with the error names that just look like the integer error syntax (eg
> "-EINVAL")

"(null)" stands for a dereference of a null pointer rather than for printing
the pointer itself.  This is a convention copied from glibc's printf("%s").
Either "0" or "NULL" (or "∅" if you allow cp437-subset Unicode ☺ ) wouldn't
cause such confusion.


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-- 
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