[ovs-dev] [strings 3/3] util: New function ovs_strzcpy().

Ben Pfaff blp at nicira.com
Tue Feb 22 19:01:43 UTC 2011


Static analyzers hate strncpy().  This new function shares its property of
initializing an entire buffer, without its nasty habit of failing to
null-terminate long strings.
---
 lib/automake.mk    |    1 +
 lib/netdev-linux.c |   16 ++++++++--------
 lib/socket-util.c  |    3 +--
 lib/util.c         |   24 +++++++++++++++++++++++-
 lib/util.h         |    3 ++-
 5 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/lib/automake.mk b/lib/automake.mk
index 2758d36..5da1971 100644
--- a/lib/automake.mk
+++ b/lib/automake.mk
@@ -137,6 +137,7 @@ lib_libopenvswitch_a_SOURCES = \
 	lib/stream.h \
 	lib/stress.c \
 	lib/stress.h \
+	lib/string.c \
 	lib/string.h \
 	lib/svec.c \
 	lib/svec.h \
diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c
index 1428ce6..0aceb45 100644
--- a/lib/netdev-linux.c
+++ b/lib/netdev-linux.c
@@ -563,7 +563,7 @@ netdev_linux_create_tap(const struct netdev_class *class OVS_UNUSED,
 
     /* Create tap device. */
     ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
-    strncpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
+    ovs_strzcpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
     if (ioctl(state->fd, TUNSETIFF, &ifr) == -1) {
         VLOG_WARN("%s: creating tap device failed: %s", name,
                   strerror(errno));
@@ -1924,7 +1924,7 @@ do_set_addr(struct netdev *netdev,
             int ioctl_nr, const char *ioctl_name, struct in_addr addr)
 {
     struct ifreq ifr;
-    strncpy(ifr.ifr_name, netdev_get_name(netdev), sizeof ifr.ifr_name);
+    ovs_strzcpy(ifr.ifr_name, netdev_get_name(netdev), sizeof ifr.ifr_name);
     make_in4_sockaddr(&ifr.ifr_addr, addr);
 
     return netdev_linux_do_ioctl(netdev_get_name(netdev), &ifr, ioctl_nr,
@@ -2051,7 +2051,7 @@ netdev_linux_arp_lookup(const struct netdev *netdev,
     memcpy(&r.arp_pa, &sin, sizeof sin);
     r.arp_ha.sa_family = ARPHRD_ETHER;
     r.arp_flags = 0;
-    strncpy(r.arp_dev, netdev_get_name(netdev), sizeof r.arp_dev);
+    ovs_strzcpy(r.arp_dev, netdev_get_name(netdev), sizeof r.arp_dev);
     COVERAGE_INC(netdev_arp_lookup);
     retval = ioctl(af_inet_sock, SIOCGARP, &r) < 0 ? errno : 0;
     if (!retval) {
@@ -4054,7 +4054,7 @@ do_get_ifindex(const char *netdev_name)
 {
     struct ifreq ifr;
 
-    strncpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
+    ovs_strzcpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
     COVERAGE_INC(netdev_get_ifindex);
     if (ioctl(af_inet_sock, SIOCGIFINDEX, &ifr) < 0) {
         VLOG_WARN_RL(&rl, "ioctl(SIOCGIFINDEX) on %s device failed: %s",
@@ -4089,7 +4089,7 @@ get_etheraddr(const char *netdev_name, uint8_t ea[ETH_ADDR_LEN])
     int hwaddr_family;
 
     memset(&ifr, 0, sizeof ifr);
-    strncpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
+    ovs_strzcpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
     COVERAGE_INC(netdev_get_hwaddr);
     if (ioctl(af_inet_sock, SIOCGIFHWADDR, &ifr) < 0) {
         VLOG_ERR("ioctl(SIOCGIFHWADDR) on %s device failed: %s",
@@ -4112,7 +4112,7 @@ set_etheraddr(const char *netdev_name, int hwaddr_family,
     struct ifreq ifr;
 
     memset(&ifr, 0, sizeof ifr);
-    strncpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
+    ovs_strzcpy(ifr.ifr_name, netdev_name, sizeof ifr.ifr_name);
     ifr.ifr_hwaddr.sa_family = hwaddr_family;
     memcpy(ifr.ifr_hwaddr.sa_data, mac, ETH_ADDR_LEN);
     COVERAGE_INC(netdev_set_hwaddr);
@@ -4131,7 +4131,7 @@ netdev_linux_do_ethtool(const char *name, struct ethtool_cmd *ecmd,
     struct ifreq ifr;
 
     memset(&ifr, 0, sizeof ifr);
-    strncpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
+    ovs_strzcpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
     ifr.ifr_data = (caddr_t) ecmd;
 
     ecmd->cmd = cmd;
@@ -4154,7 +4154,7 @@ static int
 netdev_linux_do_ioctl(const char *name, struct ifreq *ifr, int cmd,
                       const char *cmd_name)
 {
-    strncpy(ifr->ifr_name, name, sizeof ifr->ifr_name);
+    ovs_strzcpy(ifr->ifr_name, name, sizeof ifr->ifr_name);
     if (ioctl(af_inet_sock, cmd, ifr) == -1) {
         VLOG_DBG_RL(&rl, "%s: ioctl(%s) failed: %s", name, cmd_name,
                      strerror(errno));
diff --git a/lib/socket-util.c b/lib/socket-util.c
index 275bf30..e0f34e7 100644
--- a/lib/socket-util.c
+++ b/lib/socket-util.c
@@ -233,8 +233,7 @@ static void
 make_sockaddr_un__(const char *name, struct sockaddr_un *un, socklen_t *un_len)
 {
     un->sun_family = AF_UNIX;
-    strncpy(un->sun_path, name, sizeof un->sun_path);
-    un->sun_path[sizeof un->sun_path - 1] = '\0';
+    ovs_strzcpy(un->sun_path, name, sizeof un->sun_path);
     *un_len = (offsetof(struct sockaddr_un, sun_path)
                 + strlen (un->sun_path) + 1);
 }
diff --git a/lib/util.c b/lib/util.c
index 1aa8271..f784f03 100644
--- a/lib/util.c
+++ b/lib/util.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -149,6 +149,28 @@ ovs_strlcpy(char *dst, const char *src, size_t size)
     }
 }
 
+/* Copies 'src' to 'dst'.  Reads no more than 'size - 1' bytes from 'src'.
+ * Always null-terminates 'dst' (if 'size' is nonzero), and writes a zero byte
+ * to every otherwise unused byte in 'dst'.
+ *
+ * Except for performance, the following call:
+ *     ovs_strzcpy(dst, src, size);
+ * is equivalent to these two calls:
+ *     memset(dst, '\0', size);
+ *     ovs_strlcpy(dst, src, size);
+ *
+ * (Thus, ovs_strzcpy() is similar to strncpy() without some of the pitfalls.)
+ */
+void
+ovs_strzcpy(char *dst, const char *src, size_t size)
+{
+    if (size > 0) {
+        size_t len = strnlen(src, size - 1);
+        memcpy(dst, src, len);
+        memset(dst + len, '\0', size - len);
+    }
+}
+
 void
 ovs_fatal(int err_no, const char *format, ...)
 {
diff --git a/lib/util.h b/lib/util.h
index f3bf80c..e741067 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -133,6 +133,7 @@ char *xvasprintf(const char *format, va_list) PRINTF_FORMAT(1, 0) MALLOC_LIKE;
 void *x2nrealloc(void *p, size_t *n, size_t s);
 
 void ovs_strlcpy(char *dst, const char *src, size_t size);
+void ovs_strzcpy(char *dst, const char *src, size_t size);
 
 void ovs_fatal(int err_no, const char *format, ...)
     PRINTF_FORMAT(2, 3) NO_RETURN;
-- 
1.7.1





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