evm: add evm_inode_setattr to prevent updating an invalid security.evm
Permit changing of security.evm only when valid, unless in fixmode.
Reported-by: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 94d66af..8fc5b5d 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -278,6 +278,21 @@
}
/**
+ * evm_inode_setattr - prevent updating an invalid EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ */
+int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
+{
+ unsigned int ia_valid = attr->ia_valid;
+ enum integrity_status evm_status;
+
+ if (ia_valid & ~(ATTR_MODE | ATTR_UID | ATTR_GID))
+ return 0;
+ evm_status = evm_verify_current_integrity(dentry);
+ return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
+}
+
+/**
* evm_inode_post_setattr - update 'security.evm' after modifying metadata
* @dentry: pointer to the affected dentry
* @ia_valid: for the UID and GID status