linux-kernel - Re: printk()s of user-supplied strings

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Message-ID: <m3sljhp0rs.fsf@defiant.localdomain>
Date:	Mon, 28 Aug 2006 13:17:43 +0200
From:	Krzysztof Halasa <khc@...waw.pl>
To:	Willy Tarreau <w@....eu>
Cc:	Solar Designer <solar@...nwall.com>,
	Ernie Petrides <petrides@...hat.com>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: printk()s of user-supplied strings

Willy Tarreau <w@....eu> writes:

> Well, I'm not sure about this. Nearly all patches which get merged pass
> through a public review first, and when you see how many replies you get
> for and 'else' and and 'if' on two different lines, I expect lots of
> spontaneous replies such as "use %S for user-supplied strings".

I wouldn't rely on that.

>> A solution would be to normally use "%S" and only use
>> "%s" where "%S" wouldn't work.  In that case, we could as well swap "%s"
>> and "%S", though - hardening the existing "%s" and introducing "%S" for
>> those callers that depend on the old behavior.

I think it's the way to go.

> I'd rather not change "%s" semantics if we introduce another specifier
> which does exactly what we would expect "%s" to do.

Both would be equivalent in most cases. It's better to use "%s" for
most cases (either secured or not) and leave "%S" for the bunch of
special cases whose authors better know what are they doing.

> I will try your proposal to retain the trailing '\n' unescaped.

I think with "%s" and "%S" this is no longer needed.
-- 
Krzysztof Halasa
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