[PATCH 4.15 001/122] vsprintf: avoid misleading "(null)" for %px

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Adam Borowski <kilobyte@xxxxxxxxxx>

commit 3a129cc2151425e5aeb69aeb25fbc994ec738137 upstream.

Like %pK already does, print "00000000" instead.

This confused people -- the convention is that "(null)" means you tried to
dereference a null pointer as opposed to printing the address.

Link: http://lkml.kernel.org/r/20180204174521.21383-1-kilobyte@xxxxxxxxxx
To: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
To: Steven Rostedt <rostedt@xxxxxxxxxxx>
To: linux-kernel@xxxxxxxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Roberts, William C" <william.c.roberts@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: Adam Borowski <kilobyte@xxxxxxxxxx>
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 lib/vsprintf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1849,7 +1849,7 @@ char *pointer(const char *fmt, char *buf
 {
 	const int default_width = 2 * sizeof(void *);
 
-	if (!ptr && *fmt != 'K') {
+	if (!ptr && *fmt != 'K' && *fmt != 'x') {
 		/*
 		 * Print (null) with the same width as a pointer so it makes
 		 * tabular output look nice.