From: David Laight <David.Laight@ACULAB.COM>
To: 'Rasmus Villemoes' <linux@rasmusvillemoes.dk>,
Joe Perches <joe@perches.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>, Stephen Kitt <steve@sk2.org>,
Kees Cook <keescook@chromium.org>,
Nitin Gote <nitin.r.gote@intel.com>,
"jannh@google.com" <jannh@google.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: RE: [PATCH 1/2] string: Add stracpy and stracpy_pad mechanisms
Date: Tue, 23 Jul 2019 15:41:27 +0000 [thread overview]
Message-ID: <5ffdbf4f87054b47a2daf23a6afabecf@AcuMS.aculab.com> (raw)
In-Reply-To: <eec901c6-ca51-89e4-1887-1ccab0288bee@rasmusvillemoes.dk>
From: Rasmus Villemoes
> Sent: 23 July 2019 07:56
...
> > +/**
> > + * stracpy - Copy a C-string into an array of char
> > + * @to: Where to copy the string, must be an array of char and not a pointer
> > + * @from: String to copy, may be a pointer or const char array
> > + *
> > + * Helper for strscpy.
> > + * Copies a maximum of sizeof(@to) bytes of @from with %NUL termination.
> > + *
> > + * Returns:
> > + * * The number of characters copied (not including the trailing %NUL)
> > + * * -E2BIG if @to is a zero size array.
>
> Well, yes, but more importantly and generally: -E2BIG if the copy
> including %NUL didn't fit. [The zero size array thing could be made into
> a build bug for these stra* variants if one thinks that might actually
> occur in real code.]
Probably better is to return the size of the destination if the copy didn't fit
(zero if the buffer is zero length).
This allows code to do repeated:
offset += str*cpy(buf + offset, src, sizeof buf - offset);
and do a final check for overflow after all the copies.
The same is true for a snprintf()like function
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2019-07-23 15:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 0:38 [PATCH 0/2] string: Add stracpy and stracpy_pad Joe Perches
2019-07-23 0:38 ` [PATCH 1/2] string: Add stracpy and stracpy_pad mechanisms Joe Perches
2019-07-23 4:35 ` Andrew Morton
2019-07-23 4:42 ` Joe Perches
2019-07-23 21:29 ` Kees Cook
2019-07-23 6:55 ` Rasmus Villemoes
2019-07-23 15:41 ` David Laight [this message]
2019-07-23 15:50 ` Joe Perches
2019-07-23 21:34 ` Kees Cook
2019-07-24 12:05 ` Yann Droneaud
2019-07-24 13:09 ` Rasmus Villemoes
2019-07-24 17:08 ` Linus Torvalds
2019-07-25 20:03 ` Kees Cook
2019-07-26 2:46 ` Joe Perches
2019-07-23 21:36 ` Kees Cook
2019-07-24 11:40 ` Joe Perches
2019-07-23 0:38 ` [PATCH 2/2] kernel-doc: core-api: Include string.h into core-api Joe Perches
2019-07-23 21:28 ` Kees Cook
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