build: fix Wlog_Error_String overflow issues

The 'Wlog_Error_String' string is defined to be 256 bytes in length,
but in two places we write into it with a format that contains a
string (wfile->w_file) that has length 1024.  This can overflow
Wlog_Error_String, as we see in the new compiler warnings from gcc
7.2.1:

 write_log.c:124:37: warning: ‘%s’ directive writing up to 1023 bytes into
 a region of size 224 [-Wformat-overflow=]
 "Could not open write_log - open(%s, %#o, %#o) failed:  %s\n",
  ^~

Fix this by increasing the length of Wlog_Error_String to 1280
characters (1024 for wfile->w_file plus 256 for the rest of the
format string), and by using snprintf() instead of sprintf() so we
are sure we don't overflow.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

diff --git a/lib/write_log.c b/lib/write_log.c
index 8c921fc54244bc456f378ecf624a62be26cb6c3d..3bfa8c7b3091b27a4b083b56ef57de08b18c3dd4 100644 (file)
--- a/lib/write_log.c
+++ b/lib/write_log.c
@@ -73,7 +73,8 @@
 /*#define PATH_MAX pathconf("/", _PC_PATH_MAX)*/
 #endif
 
-char   Wlog_Error_String[256];
+#define ERROR_STRING_LEN 1280
+char   Wlog_Error_String[ERROR_STRING_LEN];
 
 #if __STDC__
 static int     wlog_rec_pack(struct wlog_rec *wrec, char *buf, int flag);
@@ -120,7 +121,7 @@ int                 mode;
        umask(omask);
 
        if (wfile->w_afd == -1) {
-               sprintf(Wlog_Error_String,
+               snprintf(Wlog_Error_String, ERROR_STRING_LEN,
                        "Could not open write_log - open(%s, %#o, %#o) failed:  %s\n",
                        wfile->w_file, oflags, mode, strerror(errno));
                return -1;
@@ -132,7 +133,7 @@ int                 mode;
 
        oflags = O_RDWR;
        if ((wfile->w_rfd = open(wfile->w_file, oflags)) == -1) {
-               sprintf(Wlog_Error_String,
+               snprintf(Wlog_Error_String, ERROR_STRING_LEN,
                        "Could not open write log - open(%s, %#o) failed:  %s\n",
                        wfile->w_file, oflags, strerror(errno));
                close(wfile->w_afd);