Revert "ima: define '_ima' as a builtin 'trusted' keyring"

This reverts commit 217091dd7a7a1bdac027ddb7c5a25f6ac0b8e241, which
caused the following build error:

security/integrity/digsig.c:70:5: error: redefinition of ‘integrity_init_keyring’
security/integrity/integrity.h:149:12: note: previous definition of ‘integrity_init_keyring’ w
security/integrity/integrity.h:149:12: warning: ‘integrity_init_keyring’ defined but not used

reported by Krzysztof Kolasa. Mimi says:

"I made the classic mistake of requesting this patch to be upstreamed
at the last second, rather than waiting until the next open window.

At this point, the best course would probably be to revert the two
commits and fix them for the next open window"

Reported-by: Krzysztof Kolasa <[e-mail]>
Acked-by: Mimi Zohar <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

security/integrity/digsig.c

···
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/err.h>
-#include <linux/sched.h>
 #include <linux/rbtree.h>
-#include <linux/cred.h>
 #include <linux/key-type.h>
 #include <linux/digsig.h>
 
···
 
 static struct key *keyring[INTEGRITY_KEYRING_MAX];
 
-#ifdef CONFIG_IMA_TRUSTED_KEYRING
-static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
-	".evm",
-	".module",
-	".ima",
-};
-#else
 static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
 	"_evm",
 	"_module",
 	"_ima",
 };
-#endif
 
 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 			    const char *digest, int digestlen)
···
 
 	if (!keyring[id]) {
 		keyring[id] =
-		    request_key(&key_type_keyring, keyring_name[id], NULL);
+			request_key(&key_type_keyring, keyring_name[id], NULL);
 		if (IS_ERR(keyring[id])) {
 			int err = PTR_ERR(keyring[id]);
 			pr_err("no %s keyring: %d\n", keyring_name[id], err);
···
 	}
 
 	return -EOPNOTSUPP;
-}
-
-int integrity_init_keyring(const unsigned int id)
-{
-	const struct cred *cred = current_cred();
-	const struct user_struct *user = cred->user;
-
-	keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
-				    KGIDT_INIT(0), cred,
-				    ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
-				     KEY_USR_VIEW | KEY_USR_READ),
-				    KEY_ALLOC_NOT_IN_QUOTA, user->uid_keyring);
-	if (!IS_ERR(keyring[id]))
-		set_bit(KEY_FLAG_TRUSTED_ONLY, &keyring[id]->flags);
-	else
-		pr_info("Can't allocate %s keyring (%ld)\n",
-			keyring_name[id], PTR_ERR(keyring[id]));
-	return 0;
 }

security/integrity/ima/Kconfig

···
 	  For more information on integrity appraisal refer to:
 	  <http://linux-ima.sourceforge.net>
 	  If unsure, say N.
-
-config IMA_TRUSTED_KEYRING
-	bool "Require all keys on the _ima keyring be signed"
-	depends on IMA_APPRAISE && SYSTEM_TRUSTED_KEYRING
-	default y
-	help
-	   This option requires that all keys added to the _ima
-	   keyring be signed by a key on the system trusted keyring.

security/integrity/ima/ima_appraise.c

···
 	}
 	return result;
 }
-
-#ifdef CONFIG_IMA_TRUSTED_KEYRING
-static int __init init_ima_keyring(void)
-{
-	int ret;
-
-	ret = integrity_init_keyring(INTEGRITY_KEYRING_IMA);
-	return 0;
-}
-late_initcall(init_ima_keyring);
-#endif

security/integrity/integrity.h

···
 #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
 int asymmetric_verify(struct key *keyring, const char *sig,
 		      int siglen, const char *data, int datalen);
-
-int integrity_init_keyring(const unsigned int id);
 #else
 static inline int asymmetric_verify(struct key *keyring, const char *sig,
 				    int siglen, const char *data, int datalen)
 {
 	return -EOPNOTSUPP;
-}
-
-static int integrity_init_keyring(const unsigned int id)
-{
-	return 0;
 }
 #endif