linux-kernel - Re: [PATCH RFCv3 2/3] lib/vsprintf.c: make %pD print full path for file

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <113d9380-8493-1bde-9c76-992f4ce675d9@rasmusvillemoes.dk>
Date:   Tue, 15 Jun 2021 09:14:37 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Justin He <Justin.He@....com>, Petr Mladek <pmladek@...e.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH RFCv3 2/3] lib/vsprintf.c: make %pD print full path for
 file

On 15/06/2021 08.48, Justin He wrote:
> Hi Petr
> 

>>> +   /* no filling space at all */
>>> +   if (buf >= end || !buf)
>>> +           return buf + reserved_size;
>>> +
>>> +   /* small space for long name */
>>> +   if (buf < end && prepend_len < 0)
>>> +           return string_truncate(buf, end, p, dpath_len, spec);
>>
>> We need this only because we allowed to write the path behind
>> spec.field_width. Do I get it right?
> 
> Both of field_width and precision:
> "%.14pD" or "%8.14pD"

Precision is never gonna be used with %p (or any of its kernel
extensions) because gcc would tell you

foo.c:5:13: warning: precision used with ‘%p’ gnu_printf format [-Wformat=]
    5 |  printf("%.5p\n", foo);

and there's no way -Wformat is going to be turned off to allow that usage.

IOW, there's no need to add complexity to make "%.3pD" of something that
would normally print "/foo/bar" merely print "/fo", similar to what a
precision with %s would mean.

As for field width, I don't know if it's worth honouring, but IIRC the
original %pd and %pD did that (that's where we have widen_string etc. from).

Other %p extensions put the field with to some other use (e.g. the
bitmap and hex string printing), so they obviously cannot simultaneously
use it in the traditional sense.

Rasmus