Date: Mon, 15 Jul 2002 21:25:15 +0300 From: Giorgos Keramidas <keramida@FreeBSD.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: bde@zeta.org.au, des@ofug.org, freebsd-audit@FreeBSD.org Subject: Re: bin/ln & WARNS=5 Message-ID: <20020715182514.GC55859@hades.hell.gr> In-Reply-To: <20020715.090420.83279095.imp@bsdimp.com> References: <xzpele59w21.fsf@flood.ping.uio.no> <20020715202126.S40071-100000@gamplex.bde.org> <20020715111436.GD50130@hades.hell.gr> <20020715.090420.83279095.imp@bsdimp.com>
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On 2002-07-15 09:04 +0000, M. Warner Losh wrote:
> In message: <20020715111436.GD50130@hades.hell.gr>
> Giorgos Keramidas <keramida@FreeBSD.ORG> writes:
> : + if ((pathlen = snprintf(path, sizeof(path), "%s/%s",
> : + source, p)) == -1 || pathlen >= (int)sizeof(path)) {
>
> That's down right stupid.
>
> snprintf never returns a negative number. It always returns the
> number of characters that it would have used to make the string.
It's not obvious from the manpage. I haven't read the __vfprintf()
code to find out, but I assumed this is why the return type of
snprintf() was declared as `int' and not as `size_t'. If -1 is never
possible to be a return value of snprintf(), then I assumed wrong.
> The code was right before. However, maybe the following is better and
> clearer:
>
> if (strlen(source) + strlen(p) + 1 >= PATH_MAX) {
> ... ETOOLONG stuff
> }
> snprintf(...);
The format of sprintf() after the size checks is "%s/%s" and sprintf()
will need +2 bytes to store '/' and the terminating '\0'. How about
this?
%%%
Index: ln.c
===================================================================
RCS file: /home/ncvs/src/bin/ln/ln.c,v
retrieving revision 1.28
diff -u -r1.28 ln.c
--- ln.c 30 Jun 2002 05:13:54 -0000 1.28
+++ ln.c 15 Jul 2002 18:20:19 -0000
@@ -189,12 +189,12 @@
p = target;
else
++p;
- if (snprintf(path, sizeof(path), "%s/%s", source, p) >=
- sizeof(path)) {
+ if (strlen(source) + strlen(p) + 2 > sizeof path) {
errno = ENAMETOOLONG;
warn("%s", target);
return (1);
}
+ sprintf(path, "%s/%s", source, p);
source = path;
}
%%%
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