Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1

[ Upstream commit 4fcba7802c3e15a6e56e255871d6c72f829b9dd8 ]

The patch fixes:

hv_kvp_daemon.c: In function 'kvp_set_ip_info':
hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes
into a destination of size 4096

The "(unsigned int)str_len" is to avoid:

hv_kvp_daemon.c:1309:30: warning: comparison of integer expressions of
different signedness: 'int' and 'long unsigned int' [-Wsign-compare]

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
index 3965186b375a1dc372ec983f7dd561f3c6e505b0..62c9a503ae0522cca0324eea413fd0038542cf91 100644 (file)
--- a/tools/hv/hv_kvp_daemon.c
+++ b/tools/hv/hv_kvp_daemon.c
@@ -1172,6 +1172,7 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val)
        FILE *file;
        char cmd[PATH_MAX];
        char *mac_addr;
+       int str_len;
 
        /*
         * Set the configuration for the specified interface with
@@ -1295,8 +1296,18 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val)
         * invoke the external script to do its magic.
         */
 
-       snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s",
-                "hv_set_ifconfig", if_file);
+       str_len = snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s",
+                          "hv_set_ifconfig", if_file);
+       /*
+        * This is a little overcautious, but it's necessary to suppress some
+        * false warnings from gcc 8.0.1.
+        */
+       if (str_len <= 0 || (unsigned int)str_len >= sizeof(cmd)) {
+               syslog(LOG_ERR, "Cmd '%s' (len=%d) may be too long",
+                      cmd, str_len);
+               return HV_E_FAIL;
+       }
+
        if (system(cmd)) {
                syslog(LOG_ERR, "Failed to execute cmd '%s'; error: %d %s",
                                cmd, errno, strerror(errno));