Hi Fernando,
On Thu, Jul 18, 2019 at 01:01:46PM +0200, Fernando Fernandez Mancera wrote:
> Fedora 30 uses very recent gcc (version 9.1.1 20190503 (Red Hat 9.1.1-1)),
> osf produces following warnings:
>
> -Wformat-truncation warning have been introduced in the version 7.1 of gcc.
> Also, remove a unneeded address check of "tmp + 1" in nf_osf_strchr().
>
> nfnl_osf.c: In function ‘nfnl_osf_load_fingerprints’:
> nfnl_osf.c:292:39: warning: ‘%s’ directive output may be truncated writing
> up to 1023 bytes into a region of size 128 [-Wformat-truncation=]
> 292 | cnt = snprintf(obuf, sizeof(obuf), "%s,", pbeg);
> | ^~
> nfnl_osf.c:292:9: note: ‘snprintf’ output between 2 and 1025 bytes into a
> destination of size 128
> 292 | cnt = snprintf(obuf, sizeof(obuf), "%s,", pbeg);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> nfnl_osf.c:302:46: warning: ‘%s’ directive output may be truncated writing
> up to 1023 bytes into a region of size 32 [-Wformat-truncation=]
> 302 | cnt = snprintf(f.genre, sizeof(f.genre), "%s", pbeg);
> | ^~
> nfnl_osf.c:302:10: note: ‘snprintf’ output between 1 and 1024 bytes into a
> destination of size 32
> 302 | cnt = snprintf(f.genre, sizeof(f.genre), "%s", pbeg);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> nfnl_osf.c:309:49: warning: ‘%s’ directive output may be truncated writing
> up to 1023 bytes into a region of size 32 [-Wformat-truncation=]
> 309 | cnt = snprintf(f.version, sizeof(f.version), "%s", pbeg);
> | ^~
> nfnl_osf.c:309:9: note: ‘snprintf’ output between 1 and 1024 bytes into a
> destination of size 32
> 309 | cnt = snprintf(f.version, sizeof(f.version), "%s", pbeg);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> nfnl_osf.c:317:47: warning: ‘%s’ directive output may be truncated writing
> up to 1023 bytes into a region of size 32 [-Wformat-truncation=]
> 317 | snprintf(f.subtype, sizeof(f.subtype), "%s", pbeg);
> | ^~
> nfnl_osf.c:317:7: note: ‘snprintf’ output between 1 and 1024 bytes into a
> destination of size 32
> 317 | snprintf(f.subtype, sizeof(f.subtype), "%s", pbeg);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Reported-by: Florian Westphal <fw@xxxxxxxxx>
> Signed-off-by: Fernando Fernandez Mancera <ffmancera@xxxxxxxxxx>
> ---
> src/nfnl_osf.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/src/nfnl_osf.c b/src/nfnl_osf.c
> index be3fd81..c99f8f3 100644
> --- a/src/nfnl_osf.c
> +++ b/src/nfnl_osf.c
> @@ -81,7 +81,7 @@ static char *nf_osf_strchr(char *ptr, char c)
> if (tmp)
> *tmp = '\0';
>
> - while (tmp && tmp + 1 && isspace(*(tmp + 1)))
> + while (tmp && isspace(*(tmp + 1)))
> tmp++;
>
> return tmp;
> @@ -212,7 +212,7 @@ static int osf_load_line(char *buffer, int len, int del,
> struct netlink_ctx *ctx)
> {
> int i, cnt = 0;
> - char obuf[MAXOPTSTRLEN];
> + char obuf[MAXOPTSTRLEN + 1];
> struct nf_osf_user_finger f;
> char *pbeg, *pend;
> struct nlmsghdr *nlh;
> @@ -289,7 +289,7 @@ static int osf_load_line(char *buffer, int len, int del,
> pend = nf_osf_strchr(pbeg, OSFPDEL);
> if (pend) {
> *pend = '\0';
> - cnt = snprintf(obuf, sizeof(obuf), "%s,", pbeg);
> + cnt = snprintf(obuf, sizeof(obuf), "%.128s", pbeg);
Not a big deal, but sizeof() and hard-coding the "precision" doesn't mix
well in my opinion. I've solved this like so:
i = sizeof(obuf);
cnt = snprintf(obuf, i, "%.*s,", i - 2, pbeg);
(i - 2) to leave space for the trailing comma and nul-char. Also note
that your patch drops the trailing comma, I guess that's a bug.
Maybe you want to have a look at my patch (Message-ID
20190720185226.8876-2-phil@xxxxxx) and incorporate what's useful into
yours? It's your code, so you should know better how to fix things. :)
Thanks, Phil
