ima: Move IMA-Appraisal to LSM infrastructure

A few additional IMA hooks are needed to reset the cached appraisal
status, causing the file's integrity to be re-evaluated on next access.
Register these IMA-appraisal only functions separately from the rest of IMA
functions, as appraisal is a separate feature not necessarily enabled in
the kernel configuration.

Reuse the same approach as for other IMA functions, move hardcoded calls
from various places in the kernel to the LSM infrastructure. Declare the
functions as static and register them as hook implementations in
init_ima_appraise_lsm(), called by init_ima_lsm().

Also move the inline function ima_inode_remove_acl() from the public ima.h
header to ima_appraise.c.

Signed-off-by: Roberto Sassu <[e-mail]>
Reviewed-by: Stefan Berger <[e-mail]>
Reviewed-by: Mimi Zohar <[e-mail]>
Reviewed-by: Casey Schaufler <[e-mail]>
Acked-by: Christian Brauner <[e-mail]>
Acked-by: Mimi Zohar <[e-mail]>
Signed-off-by: Paul Moore <[e-mail]>

fs/attr.c

···
 #include <linux/filelock.h>
 #include <linux/security.h>
 #include <linux/evm.h>
-#include <linux/ima.h>
 
 #include "internal.h"
 
···
 	if (!error) {
 		fsnotify_change(dentry, ia_valid);
 		security_inode_post_setattr(idmap, dentry, ia_valid);
-		ima_inode_post_setattr(idmap, dentry, ia_valid);
 		evm_inode_post_setattr(idmap, dentry, ia_valid);
 	}
 

include/linux/ima.h

···
 
 #ifdef CONFIG_IMA_APPRAISE
 extern bool is_ima_appraise_enabled(void);
-extern void ima_inode_post_setattr(struct mnt_idmap *idmap,
-				   struct dentry *dentry, int ia_valid);
-extern int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
-			      const char *xattr_name, const void *xattr_value,
-			      size_t xattr_value_len, int flags);
-extern int ima_inode_set_acl(struct mnt_idmap *idmap,
-			     struct dentry *dentry, const char *acl_name,
-			     struct posix_acl *kacl);
-static inline int ima_inode_remove_acl(struct mnt_idmap *idmap,
-				       struct dentry *dentry,
-				       const char *acl_name)
-{
-	return ima_inode_set_acl(idmap, dentry, acl_name, NULL);
-}
-
-extern int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
-				 const char *xattr_name);
 #else
 static inline bool is_ima_appraise_enabled(void)
-{
-	return 0;
-}
-
-static inline void ima_inode_post_setattr(struct mnt_idmap *idmap,
-					  struct dentry *dentry, int ia_valid)
-{
-	return;
-}
-
-static inline int ima_inode_setxattr(struct mnt_idmap *idmap,
-				     struct dentry *dentry,
-				     const char *xattr_name,
-				     const void *xattr_value,
-				     size_t xattr_value_len,
-				     int flags)
-{
-	return 0;
-}
-
-static inline int ima_inode_set_acl(struct mnt_idmap *idmap,
-				    struct dentry *dentry, const char *acl_name,
-				    struct posix_acl *kacl)
-{
-
-	return 0;
-}
-
-static inline int ima_inode_removexattr(struct mnt_idmap *idmap,
-					struct dentry *dentry,
-					const char *xattr_name)
-{
-	return 0;
-}
-
-static inline int ima_inode_remove_acl(struct mnt_idmap *idmap,
-				       struct dentry *dentry,
-				       const char *acl_name)
 {
 	return 0;
 }

security/integrity/ima/ima.h

···
 				 int xattr_len);
 int ima_read_xattr(struct dentry *dentry,
 		   struct evm_ima_xattr_data **xattr_value, int xattr_len);
+void __init init_ima_appraise_lsm(const struct lsm_id *lsmid);
 
 #else
 static inline int ima_check_blacklist(struct integrity_iint_cache *iint,
···
 				 int xattr_len)
 {
 	return 0;
+}
+
+static inline void __init init_ima_appraise_lsm(const struct lsm_id *lsmid)
+{
 }
 
 #endif /* CONFIG_IMA_APPRAISE */

security/integrity/ima/ima_appraise.c

···
  * This function is called from notify_change(), which expects the caller
  * to lock the inode's i_mutex.
  */
-void ima_inode_post_setattr(struct mnt_idmap *idmap,
-			    struct dentry *dentry, int ia_valid)
+static void ima_inode_post_setattr(struct mnt_idmap *idmap,
+				   struct dentry *dentry, int ia_valid)
 {
 	struct inode *inode = d_backing_inode(dentry);
 	struct integrity_iint_cache *iint;
···
 	return -EACCES;
 }
 
-int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
-		       const char *xattr_name, const void *xattr_value,
-		       size_t xattr_value_len, int flags)
+static int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
+			      const char *xattr_name, const void *xattr_value,
+			      size_t xattr_value_len, int flags)
 {
 	const struct evm_ima_xattr_data *xvalue = xattr_value;
 	int digsig = 0;
···
 	return result;
 }
 
-int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
-		      const char *acl_name, struct posix_acl *kacl)
+static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
+			     const char *acl_name, struct posix_acl *kacl)
 {
 	if (evm_revalidate_status(acl_name))
 		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
···
 	return 0;
 }
 
-int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
-			  const char *xattr_name)
+static int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
+				 const char *xattr_name)
 {
 	int result;
 
···
 			result = 0;
 	}
 	return result;
+}
+
+static int ima_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
+				const char *acl_name)
+{
+	return ima_inode_set_acl(idmap, dentry, acl_name, NULL);
+}
+
+static struct security_hook_list ima_appraise_hooks[] __ro_after_init = {
+	LSM_HOOK_INIT(inode_post_setattr, ima_inode_post_setattr),
+	LSM_HOOK_INIT(inode_setxattr, ima_inode_setxattr),
+	LSM_HOOK_INIT(inode_set_acl, ima_inode_set_acl),
+	LSM_HOOK_INIT(inode_removexattr, ima_inode_removexattr),
+	LSM_HOOK_INIT(inode_remove_acl, ima_inode_remove_acl),
+};
+
+void __init init_ima_appraise_lsm(const struct lsm_id *lsmid)
+{
+	security_add_hooks(ima_appraise_hooks, ARRAY_SIZE(ima_appraise_hooks),
+			   lsmid);
 }

security/integrity/ima/ima_main.c

···
 static int __init init_ima_lsm(void)
 {
 	security_add_hooks(ima_hooks, ARRAY_SIZE(ima_hooks), &ima_lsmid);
+	init_ima_appraise_lsm(&ima_lsmid);
 	return 0;
 }
 

security/security.c

···
 #include <linux/kernel_read_file.h>
 #include <linux/lsm_hooks.h>
 #include <linux/integrity.h>
-#include <linux/ima.h>
 #include <linux/evm.h>
 #include <linux/fsnotify.h>
 #include <linux/mman.h>
···
 		ret = cap_inode_setxattr(dentry, name, value, size, flags);
 	if (ret)
 		return ret;
-	ret = ima_inode_setxattr(idmap, dentry, name, value, size, flags);
-	if (ret)
-		return ret;
 	return evm_inode_setxattr(idmap, dentry, name, value, size, flags);
 }
 
···
 		return 0;
 	ret = call_int_hook(inode_set_acl, 0, idmap, dentry, acl_name,
 			    kacl);
-	if (ret)
-		return ret;
-	ret = ima_inode_set_acl(idmap, dentry, acl_name, kacl);
 	if (ret)
 		return ret;
 	return evm_inode_set_acl(idmap, dentry, acl_name, kacl);
···
 	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
 		return 0;
 	ret = call_int_hook(inode_remove_acl, 0, idmap, dentry, acl_name);
-	if (ret)
-		return ret;
-	ret = ima_inode_remove_acl(idmap, dentry, acl_name);
 	if (ret)
 		return ret;
 	return evm_inode_remove_acl(idmap, dentry, acl_name);
···
 	ret = call_int_hook(inode_removexattr, 1, idmap, dentry, name);
 	if (ret == 1)
 		ret = cap_inode_removexattr(idmap, dentry, name);
-	if (ret)
-		return ret;
-	ret = ima_inode_removexattr(idmap, dentry, name);
 	if (ret)
 		return ret;
 	return evm_inode_removexattr(idmap, dentry, name);