linux-kernel - Re: revert "fs/befs/linuxvfs.c: replace strncpy by strlcpy"

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Date:	Tue, 28 Apr 2015 13:51:42 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Fabian Frederick <fabf@...net.be>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
Subject: Re: revert "fs/befs/linuxvfs.c: replace strncpy by strlcpy"

On Tue, Apr 28, 2015 at 12:48 PM, Chris Metcalf <cmetcalf@...hip.com> wrote:
>
> FWIW, I wanted to deal with some strncpy/strlcpy API issues last year
> and just put a "strscpy()" function in arch/tile/gxio/mpipe.c,

So quite frankly, I don't like that one either.

Some people really *do* want truncation, and your strscpy() makes that
impossible.

Also, your strscpy() implementation is actually not thread-safe: it
can return an non-terminated string if the source string isn't stable.
That can certainly be a design issue ("don't do that then"), but it
*can* be a possible source of security issues, so it's a bad idea in
something that is supposed to be secure.

And quite frankly, I think that the *only* valid reason to add another
random string copy function is that you actually get it right. We
don't need yet another half-arsed routine that can be easily misused.
We have too many of those.

                          Linus
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