[PATCH iptables v2] nfnl_osf: fix snprintf -Wformat-truncation warning

[PATCH iptables v2] nfnl_osf: fix snprintf -Wformat-truncation warning

[Fernando Fernandez Mancera]

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:346:33: warning: ‘%s’ directive output may be truncated writing
up to 1023 bytes into a region of size 128 [-Wformat-truncation=]
  346 |   snprintf(obuf, sizeof(obuf), "%s,", pbeg);
      |                                 ^~
nfnl_osf.c:346:3: note: ‘snprintf’ output between 2 and 1025 bytes into a
destination of size 128
  346 |   snprintf(obuf, sizeof(obuf), "%s,", pbeg);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
nfnl_osf.c:354:40: warning: ‘%s’ directive output may be truncated writing
up to 1023 bytes into a region of size 32 [-Wformat-truncation=]
  354 |    snprintf(f.genre, sizeof(f.genre), "%s", pbeg);
      |                                        ^~
nfnl_osf.c:354:4: note: ‘snprintf’ output between 1 and 1024 bytes into a
destination of size 32
  354 |    snprintf(f.genre, sizeof(f.genre), "%s", pbeg);
      |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
nfnl_osf.c:363:43: warning: ‘%s’ directive output may be truncated writing
up to 1023 bytes into a region of size 32 [-Wformat-truncation=]
  363 |   snprintf(f.version, sizeof(f.version), "%s", pbeg);
      |                                           ^~
nfnl_osf.c:363:3: note: ‘snprintf’ output between 1 and 1024 bytes into a
destination of size 32
  363 |   snprintf(f.version, sizeof(f.version), "%s", pbeg);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
nfnl_osf.c:370:47: warning: ‘%s’ directive output may be truncated writing
up to 1023 bytes into a region of size 32 [-Wformat-truncation=]
  370 |       snprintf(f.subtype, sizeof(f.subtype), "%s", pbeg);
      |                                               ^~
nfnl_osf.c:370:7: note: ‘snprintf’ output between 1 and 1024 bytes into a
destination of size 32
  370 |       snprintf(f.subtype, sizeof(f.subtype), "%s", pbeg);
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 utils/nfnl_osf.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/utils/nfnl_osf.c b/utils/nfnl_osf.c
index 0ea33fce..15d53197 100644
--- a/utils/nfnl_osf.c
+++ b/utils/nfnl_osf.c
@@ -343,31 +343,34 @@ static int osf_load_line(char *buffer, int len, int del)
 	pend = xt_osf_strchr(pbeg, OSFPDEL);
 	if (pend) {
 		*pend = '\0';
-		snprintf(obuf, sizeof(obuf), "%s,", pbeg);
+		i = sizeof(obuf);
+		snprintf(obuf, i, "%.*s,", i - 2, pbeg);
 		pbeg = pend + 1;
 	}
 
 	pend = xt_osf_strchr(pbeg, OSFPDEL);
 	if (pend) {
 		*pend = '\0';
+		i = sizeof(f.genre);
 		if (pbeg[0] == '@' || pbeg[0] == '*')
-			snprintf(f.genre, sizeof(f.genre), "%s", pbeg + 1);
-		else
-			snprintf(f.genre, sizeof(f.genre), "%s", pbeg);
+			pbeg++;
+		snprintf(f.genre, i, "%.*s", i - 1, pbeg);
 		pbeg = pend + 1;
 	}
 
 	pend = xt_osf_strchr(pbeg, OSFPDEL);
 	if (pend) {
 		*pend = '\0';
-		snprintf(f.version, sizeof(f.version), "%s", pbeg);
+		i = sizeof(f.version);
+		snprintf(f.version, i, "%.*s", i - 1, pbeg);
 		pbeg = pend + 1;
 	}
 
 	pend = xt_osf_strchr(pbeg, OSFPDEL);
 	if (pend) {
 		*pend = '\0';
-		snprintf(f.subtype, sizeof(f.subtype), "%s", pbeg);
+		i = sizeof(f.subtype);
+		snprintf(f.subtype, i, "%.*s", i - 1, pbeg);
 	}
 
 	xt_osf_parse_opt(f.opt, &f.opt_num, obuf, sizeof(obuf));
-- 
2.20.1

Re: [PATCH iptables v2] nfnl_osf: fix snprintf -Wformat-truncation warning

[Pablo Neira Ayuso]

On Wed, Jul 24, 2019 at 09:31:14AM +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().

Applied, thanks Fernando.