[3/3] xfstests: fix Wlog_Error_String overflow issues

Commit Message

Ross Zwisler Dec. 7, 2017, 9:35 p.m. UTC

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 <[e-mail]>
---
 lib/write_log.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Patch

diff --git a/lib/write_log.c b/lib/write_log.c
index 8c921fc5..3bfa8c7b 100644
--- 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);