From: Petr Tesarik <ptesarik@suse.cz>
Subject: Fix string append in dump_log_entry()
References: bnc#865596
Patch-mainline: not yet

To quote the sprintf(3) man page:

    Some programs imprudently rely on code such as the following

        sprintf(buf, "%s some further text", buf);

    to append text to buf.  However, the standards explicitly note that
    the results are undefined if source and destination buffers overlap
    when calling sprintf(), snprintf(), vsprintf(), and vsnprintf().
    Depending on the version of gcc(1) used, and the compiler options
    employed, calls such as the above will not produce the expected results.

It's also overkill to call sprintf() for something that can be done
with a simple assignment.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
---
 makedumpfile.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3830,7 +3830,7 @@ reset_bitmap_of_free_pages(unsigned long
 static int
 dump_log_entry(char *logptr, int fp)
 {
-	char *msg, *p;
+	char *msg, *p, *bufp;
 	unsigned int i, text_len;
 	unsigned long long ts_nsec;
 	char buf[BUFSIZE];
@@ -3845,20 +3845,21 @@ dump_log_entry(char *logptr, int fp)
 
 	msg = logptr + SIZE(printk_log);
 
-	sprintf(buf, "[%5lld.%06ld] ", nanos, rem/1000);
+	bufp = buf;
+	bufp += sprintf(buf, "[%5lld.%06ld] ", nanos, rem/1000);
 
 	for (i = 0, p = msg; i < text_len; i++, p++) {
 		if (*p == '\n')
-			sprintf(buf, "%s.", buf);
+			*bufp++ = '.';
 		else if (isprint(*p) || isspace(*p))
-			sprintf(buf, "%s%c", buf, *p);
+			*bufp++ = *p;
 		else
-			sprintf(buf, "%s.", buf);
+			*bufp++ = '.';
 	}
 
-	sprintf(buf, "%s\n", buf);
+	*bufp++ = '\n';
 
-	if (write(info->fd_dumpfile, buf, strlen(buf)) < 0)
+	if (write(info->fd_dumpfile, buf, bufp - buf) < 0)
 		return FALSE;
 	else
 		return TRUE;