if

module/os/linux/zfs/zpl_xattr.c

@@ -1514,21 +1514,14 @@ zpl_permission(struct inode *ip, int mask)
 	}
 
 	/*
-	 * Fast path for execute checks. This is not authoritative as user may
-	 * have explicit entry granting execute or be member of group granting
-	 * execute.
+	 * Fast path for execute checks. Do not use zfs_fastaccesschk_execute
+	 * since it may end up granting execute access in presence of explicit
+	 * deny entry for user / group, and it also read the ZFS ACL
+	 * (non-cached) which we wish to avoid in RCU.
 	 */
-	if (to_check == ACE_EXECUTE) {
-#if defined(HAVE_IOPS_PERMISSION_USERNS)
-		if ((ITOZ(ip)->z_pflags & ZFS_NO_EXECS_DENIED) ||
-		    (generic_permission(userns, ip, mask) == 0)) {
-#else
-		if ((ITOZ(ip)->z_pflags & ZFS_NO_EXECS_DENIED) ||
-		    (generic_permission(ip, mask) == 0)) {
-#endif
+	if ((to_check == ACE_EXECUTE) &&
+	    (ITOZ(ip)->z_pflags & ZFS_NO_EXECS_DENIED))
 			return (0);
-		}
-	}
 
 	/*
 	 * inode permission operation may be called in rcu-walk mode
@@ -1538,10 +1531,6 @@ zpl_permission(struct inode *ip, int mask)
 	 * If a situation is encountered that rcu-walk cannot handle,
 	 * return -ECHILD and it will be called again in ref-walk mode.
 	 */
-	if (mask & MAY_NOT_BLOCK) {
-		return (-ECHILD);
-	}
-
 	cr = CRED();
 	crhold(cr);
 
@@ -1590,6 +1579,11 @@ zpl_permission(struct inode *ip, int mask)
 		return (0);
 	}
 
+	if (mask & MAY_NOT_BLOCK) {
+		crfree(cr);
+		return (-ECHILD);
+	}
+
 	ret = -zfs_access(ITOZ(ip), to_check, V_ACE_MASK, cr);
 	crfree(cr);
 	return (ret);