netdev - [iproute PATCH 28/51] nstat: Avoid passing negative fd to fdopen()

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Message-Id: <20170812120510.28750-29-phil@nwl.cc>
Date:   Sat, 12 Aug 2017 14:04:47 +0200
From:   Phil Sutter <phil@....cc>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: [iproute PATCH 28/51] nstat: Avoid passing negative fd to fdopen()

Introduce a wrapper which does the sanity checking and returns NULL
in case fd is invalid.

Signed-off-by: Phil Sutter <phil@....cc>
---
 misc/nstat.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/misc/nstat.c b/misc/nstat.c
index 23e1569d7872b..c1e7ddec271e2 100644
--- a/misc/nstat.c
+++ b/misc/nstat.c
@@ -252,9 +252,16 @@ static void load_ugly_table(FILE *fp)
 	}
 }
 
+static FILE *fdopen_null(int fd, const char *mode)
+{
+	if (fd < 0)
+		return NULL;
+	return fdopen(fd, mode);
+}
+
 static void load_sctp_snmp(void)
 {
-	FILE *fp = fdopen(net_sctp_snmp_open(), "r");
+	FILE *fp = fdopen_null(net_sctp_snmp_open(), "r");
 
 	if (fp) {
 		load_good_table(fp);
@@ -264,7 +271,7 @@ static void load_sctp_snmp(void)
 
 static void load_snmp(void)
 {
-	FILE *fp = fdopen(net_snmp_open(), "r");
+	FILE *fp = fdopen_null(net_snmp_open(), "r");
 
 	if (fp) {
 		load_ugly_table(fp);
@@ -274,7 +281,7 @@ static void load_snmp(void)
 
 static void load_snmp6(void)
 {
-	FILE *fp = fdopen(net_snmp6_open(), "r");
+	FILE *fp = fdopen_null(net_snmp6_open(), "r");
 
 	if (fp) {
 		load_good_table(fp);
@@ -284,7 +291,7 @@ static void load_snmp6(void)
 
 static void load_netstat(void)
 {
-	FILE *fp = fdopen(net_netstat_open(), "r");
+	FILE *fp = fdopen_null(net_netstat_open(), "r");
 
 	if (fp) {
 		load_ugly_table(fp);
-- 
2.13.1