KVM: Fix infinite loop in ptr2hex()

Right shift larger than the left operand size are undefined.
This can cause infinite loop in ptr2hex() if the highest nibble
in the second argument is non-zero. Use temporary variable to avoid
bit-shifting by large values.

Reviewed-by: Cyril Hrubis <[email protected]>
Reviewed-by: Petr Vorel <[email protected]>
Signed-off-by: Martin Doucha <[email protected]>

Author: mdoucha

testcases/kernel/kvm/lib_guest.c

@@ -82,7 +82,7 @@ char *ptr2hex(char *dest, uintptr_t val)
 	uintptr_t tmp;
 	char *ret = dest;
 
-	for (i = 4; val >> i; i += 4)
+	for (i = 4, tmp = val >> 4; tmp; i += 4, tmp >>= 4)
 		;
 
 	do {