LSM: SafeSetID: refactor policy hash table

parent_kuid and child_kuid are kuids, there is no reason to make them
uint64_t. (And anyway, in the kernel, the normal name for that would be
u64, not uint64_t.)

check_setuid_policy_hashtable_key() and
check_setuid_policy_hashtable_key_value() are basically the same thing,
merge them.

Also fix the comment that claimed that (1<<8)==128.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>

security/safesetid/lsm.h

@@ -15,6 +15,8 @@
 #define _SAFESETID_H
 
 #include <linux/types.h>
+#include <linux/uidgid.h>
+#include <linux/hashtable.h>
 
 /* Flag indicating whether initialization completed */
 extern int safesetid_initialized;
@@ -25,6 +27,23 @@ enum safesetid_whitelist_file_write_type {
 	SAFESETID_WHITELIST_FLUSH, /* Flush whitelist policies. */
 };
 
+enum sid_policy_type {
+	SIDPOL_DEFAULT, /* source ID is unaffected by policy */
+	SIDPOL_CONSTRAINED, /* source ID is affected by policy */
+	SIDPOL_ALLOWED /* target ID explicitly allowed */
+};
+
+/*
+ * Hash table entry to store safesetid policy signifying that 'src_uid'
+ * can setid to 'dst_uid'.
+ */
+struct entry {
+	struct hlist_node next;
+	struct hlist_node dlist; /* for deletion cleanup */
+	kuid_t src_uid;
+	kuid_t dst_uid;
+};
+
 /* Add entry to safesetid whitelist to allow 'parent' to setid to 'child'. */
 int add_safesetid_whitelist_entry(kuid_t parent, kuid_t child);