[nft] src: osf: fix snprintf -Wformat-truncation warning
diff mbox series

Message ID 20190718110145.13361-1-ffmancera@riseup.net
State Changes Requested
Delegated to: Pablo Neira
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Series
  • [nft] src: osf: fix snprintf -Wformat-truncation warning
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Commit Message

Fernando Fernandez Mancera July 18, 2019, 11:01 a.m. UTC
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@strlen.de>
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 src/nfnl_osf.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Comments

Phil Sutter July 20, 2019, 8:21 p.m. UTC | #1
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@strlen.de>
> Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
> ---
>  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@nwl.cc) and incorporate what's useful into
yours? It's your code, so you should know better how to fix things. :)

Thanks, Phil
Fernando Fernandez Mancera July 21, 2019, 9:59 a.m. UTC | #2
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@strlen.de>
>> Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
>> ---
>>  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@nwl.cc) 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!
Phil Sutter July 21, 2019, 10:43 a.m. UTC | #3
Hi,

On Sun, Jul 21, 2019 at 11:59:14AM +0200, Fernando Fernandez Mancera wrote:
[...]
> 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.

Sounds great, thanks a lot!

Cheers, Phil

Patch
diff mbox series

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);
 		pbeg = pend + 1;
 	}
 
@@ -297,16 +297,16 @@  static int osf_load_line(char *buffer, int len, int del,
 	if (pend) {
 		*pend = '\0';
 		if (pbeg[0] == '@' || pbeg[0] == '*')
-			cnt = snprintf(f.genre, sizeof(f.genre), "%s", pbeg + 1);
+			cnt = snprintf(f.genre, sizeof(f.genre), "%.31s", pbeg + 1);
 		else
-			cnt = snprintf(f.genre, sizeof(f.genre), "%s", pbeg);
+			cnt = snprintf(f.genre, sizeof(f.genre), "%.31s", pbeg);
 		pbeg = pend + 1;
 	}
 
 	pend = nf_osf_strchr(pbeg, OSFPDEL);
 	if (pend) {
 		*pend = '\0';
-		cnt = snprintf(f.version, sizeof(f.version), "%s", pbeg);
+		cnt = snprintf(f.version, sizeof(f.version), "%.31s", pbeg);
 		pbeg = pend + 1;
 	}
 
@@ -314,7 +314,7 @@  static int osf_load_line(char *buffer, int len, int del,
 	if (pend) {
 		*pend = '\0';
 		cnt =
-		    snprintf(f.subtype, sizeof(f.subtype), "%s", pbeg);
+		    snprintf(f.subtype, sizeof(f.subtype), "%.31s", pbeg);
 		pbeg = pend + 1;
 	}