On Wed, 2021-04-07 at 09:17 -0700, Casey Schaufler wrote:

quoted

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 565e33ff19d0..1f029e4c8d7f 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c

@@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
      if (result == 1) {
              if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
                      return -EINVAL;
-             ima_reset_appraise_flags(d_backing_inode(dentry),
-                     xvalue->type == EVM_IMA_XATTR_DIGSIG);
              result = 0;
      }
      return result;
 }
 
+void ima_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
+                          const void *xattr_value, size_t xattr_value_len)
+{
+     const struct evm_ima_xattr_data *xvalue = xattr_value;
+     int result;
+
+     result = ima_protect_xattr(dentry, xattr_name, xattr_value,
+                                xattr_value_len);
+     if (result == 1)
+             ima_reset_appraise_flags(d_backing_inode(dentry),
+                     xvalue->type == EVM_IMA_XATTR_DIGSIG);
+}
+

Now you're calling ima_protect_xattr() twice for each setxattr.
Is that safe? Is it performant? Does it matter?

The first time the call to ima_protect_xattr() prevents the
security.ima from being inappropriately modified.  The second time it
resets the cached status flags.  From a performance perspective,
unnecessarily re-calcuating the file hash is worse than rechecking the
security xattr string.
 
Mimi