From: Guy Harris <guy@alum.mit.edu>
Date: Thu, 1 Dec 2011 06:45:03 +0000 (-0800)
Subject: Don't drive on if fopen() or opendir() returns NULL.
X-Git-Tag: libpcap-1.3-bp~28
X-Git-Url: https://git.tcpdump.org/libpcap/commitdiff_plain/bd93f801f1232508fcba3f8c2c5fe4f4372d3a49

Don't drive on if fopen() or opendir() returns NULL.

Always either return 0, for "I can't scan that sysfs/procfs file because
it doesn't exist", if the error is ENOENT, and return -1 with an error
message for all other errors.

Thanks to Michal Sekletar for finding that.
---

diff --git a/pcap-linux.c b/pcap-linux.c
index cedc2caf..873a066e 100644
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -1890,8 +1890,20 @@ scan_sys_class_net(pcap_if_t **devlistp, char *errbuf)
 	int ret = 1;
 
 	sys_class_net_d = opendir("/sys/class/net");
-	if (sys_class_net_d == NULL && errno == ENOENT)
-		return (0);
+	if (sys_class_net_d == NULL) {
+		/*
+		 * Don't fail if it doesn't exist at all.
+		 */
+		if (errno == ENOENT)
+			return (0);
+
+		/*
+		 * Fail if we got some other error.
+		 */
+		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+		    "Can't open /sys/class/net: %s", pcap_strerror(errno));
+		return (-1);
+	}
 
 	/*
 	 * Create a socket from which to fetch interface information.
@@ -2024,8 +2036,20 @@ scan_proc_net_dev(pcap_if_t **devlistp, char *errbuf)
 	int ret = 0;
 
 	proc_net_f = fopen("/proc/net/dev", "r");
-	if (proc_net_f == NULL && errno == ENOENT)
-		return (0);
+	if (proc_net_f == NULL) {
+		/*
+		 * Don't fail if it doesn't exist at all.
+		 */
+		if (errno == ENOENT)
+			return (0);
+
+		/*
+		 * Fail if we got some other error.
+		 */
+		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+		    "Can't open /proc/net/dev: %s", pcap_strerror(errno));
+		return (-1);
+	}
 
 	/*
 	 * Create a socket from which to fetch interface information.