Hi Phil,
On 7/20/19 10:21 PM, Phil Sutter wrote:
> 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.
>
Oh! I am really happy that you spotted the missing trailing comma,
thanks! :-)
> 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
>
I think your code is more readable than mine. I am going to send a v2
patch with your code but also adding the following fix.
- while (tmp && tmp + 1 && isspace(*(tmp + 1)))
+ while (tmp && isspace(*(tmp + 1)))
I am going to send a similar patch for the iptables tree because this
file was imported from iptables.git/utils/nfnl_osf.c.
Thanks!
