fix unreported overflow in autogerenared stream IDs

src/t_stream.c

@@ -173,9 +173,19 @@ int streamCompareID(streamID *a, streamID *b) {
  * C_ERR if an ID was given via 'use_id', but adding it failed since the
  * current top ID is greater or equal. */
 int streamAppendItem(stream *s, robj **argv, int64_t numfields, streamID *added_id, streamID *use_id) {
-    /* If an ID was given, check that it's greater than the last entry ID
-     * or return an error. */
-    if (use_id && streamCompareID(use_id,&s->last_id) <= 0) return C_ERR;
+    
+    /* Generate the new entry ID. */
+    streamID id;
+    if (use_id)
+        id = *use_id;
+    else
+        streamNextID(&s->last_id,&id);
+
+    /* Check that the new ID is greater than the last entry ID
+     * or return an error. Automatically generated IDs might
+     * overflow (and wrap-around) when incrementing the sequence 
+       part. */
+    if (streamCompareID(&id,&s->last_id) <= 0) return C_ERR;
 
     /* Add the new entry. */
     raxIterator ri;
@@ -192,13 +202,6 @@ int streamAppendItem(stream *s, robj **argv, int64_t numfields, streamID *added_
     }
     raxStop(&ri);
 
-    /* Generate the new entry ID. */
-    streamID id;
-    if (use_id)
-        id = *use_id;
-    else
-        streamNextID(&s->last_id,&id);
-
     /* We have to add the key into the radix tree in lexicographic order,
      * to do so we consider the ID as a single 128 bit number written in
      * big endian, so that the most significant bytes are the first ones. */

tests/unit/type/stream.tcl

@@ -79,6 +79,12 @@ start_server {
         assert {[streamCompareID $id2 $id3] == -1}
     }
 
+    test {XADD IDs correctly report an error when overflowing} {
+        r DEL mystream
+        r xadd mystream 18446744073709551615-18446744073709551615 a b
+        assert_error ERR* {r xadd mystream * c d}
+    }
+
     test {XADD with MAXLEN option} {
         r DEL mystream
         for {set j 0} {$j < 1000} {incr j} {