[PATCH v2 5/7] kdb: Use format-specifiers rather than memset() for padding in kdb_read()

[Daniel Thompson]

Currently when the current line should be removed from the display
kdb_read() uses memset() to fill a temporary buffer with spaces.
The problem is not that this could be trivially implemented using a
format string rather than open coding it. The real problem is that
it is possible, on systems with a long kdb_prompt_str, to write pas
the end of the tmpbuffer.

Happily, as mentioned above, this can be trivially implemented using a
format string. Make it so!

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
---
 kernel/debug/kdb/kdb_io.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index f167894b11b8e..2cd17313fe652 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -299,11 +299,9 @@ static char *kdb_read(char *buffer, size_t bufsize)
 		break;
 	case 14: /* Down */
 	case 16: /* Up */
-		memset(tmpbuffer, ' ',
-		       strlen(kdb_prompt_str) + (lastchar-buffer));
-		*(tmpbuffer+strlen(kdb_prompt_str) +
-		  (lastchar-buffer)) = '\0';
-		kdb_printf("\r%s\r", tmpbuffer);
+		kdb_printf("\r%*c\r",
+			   (int)(strlen(kdb_prompt_str) + (lastchar - buffer)),
+			   ' ');
 		*lastchar = (char)key;
 		*(lastchar+1) = '\0';
 		return lastchar;

-- 
2.43.0