evm: Pass user namespace to set/remove xattr hooks

In preparation for 'evm: Allow setxattr() and setattr() for unmodified
metadata', this patch passes mnt_userns to the inode set/remove xattr hooks
so that the GID of the inode on an idmapped mount is correctly determined
by posix_acl_update_mode().

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Author: robertosassu

include/linux/evm.h

@@ -23,13 +23,15 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
 					     struct integrity_iint_cache *iint);
 extern int evm_inode_setattr(struct dentry *dentry, struct iattr *attr);
 extern void evm_inode_post_setattr(struct dentry *dentry, int ia_valid);
-extern int evm_inode_setxattr(struct dentry *dentry, const char *name,
+extern int evm_inode_setxattr(struct user_namespace *mnt_userns,
+			      struct dentry *dentry, const char *name,
 			      const void *value, size_t size);
 extern void evm_inode_post_setxattr(struct dentry *dentry,
 				    const char *xattr_name,
 				    const void *xattr_value,
 				    size_t xattr_value_len);
-extern int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name);
+extern int evm_inode_removexattr(struct user_namespace *mnt_userns,
+				 struct dentry *dentry, const char *xattr_name);
 extern void evm_inode_post_removexattr(struct dentry *dentry,
 				       const char *xattr_name);
 extern int evm_inode_init_security(struct inode *inode,
@@ -72,7 +74,8 @@ static inline void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
 	return;
 }
 
-static inline int evm_inode_setxattr(struct dentry *dentry, const char *name,
+static inline int evm_inode_setxattr(struct user_namespace *mnt_userns,
+				     struct dentry *dentry, const char *name,
 				     const void *value, size_t size)
 {
 	return 0;
@@ -86,7 +89,8 @@ static inline void evm_inode_post_setxattr(struct dentry *dentry,
 	return;
 }
 
-static inline int evm_inode_removexattr(struct dentry *dentry,
+static inline int evm_inode_removexattr(struct user_namespace *mnt_userns,
+					struct dentry *dentry,
 					const char *xattr_name)
 {
 	return 0;

security/integrity/evm/evm_main.c

@@ -342,7 +342,8 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
  * For posix xattr acls only, permit security.evm, even if it currently
  * doesn't exist, to be updated unless the EVM signature is immutable.
  */
-static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
+static int evm_protect_xattr(struct user_namespace *mnt_userns,
+			     struct dentry *dentry, const char *xattr_name,
 			     const void *xattr_value, size_t xattr_value_len)
 {
 	enum integrity_status evm_status;
@@ -406,6 +407,7 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
 
 /**
  * evm_inode_setxattr - protect the EVM extended attribute
+ * @mnt_userns: user namespace of the idmapped mount
  * @dentry: pointer to the affected dentry
  * @xattr_name: pointer to the affected extended attribute name
  * @xattr_value: pointer to the new extended attribute value
@@ -417,8 +419,9 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
  * userspace from writing HMAC value.  Writing 'security.evm' requires
  * requires CAP_SYS_ADMIN privileges.
  */
-int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
-		       const void *xattr_value, size_t xattr_value_len)
+int evm_inode_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		       const char *xattr_name, const void *xattr_value,
+		       size_t xattr_value_len)
 {
 	const struct evm_ima_xattr_data *xattr_data = xattr_value;
 
@@ -435,27 +438,29 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 		    xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
 			return -EPERM;
 	}
-	return evm_protect_xattr(dentry, xattr_name, xattr_value,
+	return evm_protect_xattr(mnt_userns, dentry, xattr_name, xattr_value,
 				 xattr_value_len);
 }
 
 /**
  * evm_inode_removexattr - protect the EVM extended attribute
+ * @mnt_userns: user namespace of the idmapped mount
  * @dentry: pointer to the affected dentry
  * @xattr_name: pointer to the affected extended attribute name
  *
  * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
  * the current value is valid.
  */
-int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
+int evm_inode_removexattr(struct user_namespace *mnt_userns,
+			  struct dentry *dentry, const char *xattr_name)
 {
 	/* Policy permits modification of the protected xattrs even though
 	 * there's no HMAC key loaded
 	 */
 	if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
 		return 0;
 
-	return evm_protect_xattr(dentry, xattr_name, NULL, 0);
+	return evm_protect_xattr(mnt_userns, dentry, xattr_name, NULL, 0);
 }
 
 static void evm_reset_status(struct inode *inode)

security/security.c

@@ -1354,7 +1354,7 @@ int security_inode_setxattr(struct user_namespace *mnt_userns,
 	ret = ima_inode_setxattr(dentry, name, value, size);
 	if (ret)
 		return ret;
-	return evm_inode_setxattr(dentry, name, value, size);
+	return evm_inode_setxattr(mnt_userns, dentry, name, value, size);
 }
 
 void security_inode_post_setxattr(struct dentry *dentry, const char *name,
@@ -1399,7 +1399,7 @@ int security_inode_removexattr(struct user_namespace *mnt_userns,
 	ret = ima_inode_removexattr(dentry, name);
 	if (ret)
 		return ret;
-	return evm_inode_removexattr(dentry, name);
+	return evm_inode_removexattr(mnt_userns, dentry, name);
 }
 
 int security_inode_need_killpriv(struct dentry *dentry)