lib/vsprintf.c: kptr_restrict: fix pK-error in SysRq show-all-timers(Q)

When using ALT+SysRq+Q all the pointers are replaced with "pK-error" like
this:

	[23153.208033]   .base:               pK-error

with echo h > /proc/sysrq-trigger it works:

	[23107.776363]   .base:       ffff88023e60d540

The intent behind this behavior was to return "pK-error" in cases where
the %pK format specifier was used in interrupt context, because the
CAP_SYSLOG check wouldn't be meaningful.  Clearly this should only apply
when kptr_restrict is actually enabled though.

Reported-by: Stevie Trujillo <stevie.trujillo@gmail.com>
Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/vsprintf.c

@@ -1045,7 +1045,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		 * %pK cannot be used in IRQ context because its test
 		 * for CAP_SYSLOG would be meaningless.
 		 */
-		if (in_irq() || in_serving_softirq() || in_nmi()) {
+		if (kptr_restrict && (in_irq() || in_serving_softirq() ||
+				      in_nmi())) {
 			if (spec.field_width == -1)
 				spec.field_width = default_width;
 			return string(buf, end, "pK-error", spec);