[Crash-utility] [PATCH 2/2] tools: fix potential source and destination overlap with strcpy()

[HATAYAMA Daisuke]

valgrind detects the following error:

    ==14603== Source and destination overlap in strcpy(0x1ffefffe42, 0x1ffefffe44)
    ==14603==    at 0x483CD70: strcpy (vg_replace_strmem.c:511)
    ==14603==    by 0x477813: pages_to_size (tools.c:6393)
    ==14603==    by 0x4F292E: display_sys_stats (kernel.c:5629)
    ==14603==    by 0x464BC7: main_loop (main.c:797)
    ==14603==    by 0x6BE352: captured_command_loop (main.c:258)
    ==14603==    by 0x6BC959: catch_errors (exceptions.c:557)
    ==14603==    by 0x6BF3D5: captured_main (main.c:1064)
    ==14603==    by 0x6BC959: catch_errors (exceptions.c:557)
    ==14603==    by 0x6BF686: gdb_main (main.c:1079)
    ==14603==    by 0x6BF686: gdb_main_entry (main.c:1099)
    ==14603==    by 0x46316F: main (main.c:708)
    ==14603==

pages_to_size() removes ".0 " if it is contained in the created string
by overwriting them using strcpy() with the following "MB\0" or
"GB\0". However, strcpy() doesn't accept such overlapping source and
destination and thus use of strcpy() in this case is illegal.

Let's fix this by re-implementing the logic by memmove() where
destination and source strings may overlap.

Signed-off-by: HATAYAMA Daisuke <d.hatayama at fujitsu.com>
---
 tools.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/tools.c b/tools.c
index 89352b1..71bac6d 100644
--- a/tools.c
+++ b/tools.c
@@ -6371,7 +6371,7 @@ char *
 pages_to_size(ulong pages, char *buf)
 {
 	double total;
-	char *p1, *p2;
+	char *p;
 
 	if (pages == 0) {
 		sprintf(buf, "0");
@@ -6387,11 +6387,8 @@ pages_to_size(ulong pages, char *buf)
         else
         	sprintf(buf, "%ld KB", (ulong)(total/(double)KILOBYTES(1)));
 
-	if ((p1 = strstr(buf, ".0 "))) {
-		p2 = p1 + 3;
-		*p1++ = ' ';
-		strcpy(p1, p2);
-	}
+	if ((p = strstr(buf, ".0 ")))
+		memmove(p, p + 2, sizeof(" GB"));
 
 	return buf;
 }
-- 
2.29.2