HTTP/2: fix indirect reprioritization.

Previously, streams that were indirectly reprioritized (either because of
a new exclusive dependency on their parent or because of removal of their
parent from the dependency tree), didn't have their pointer to the parent
node updated.

This broke detection of circular dependencies and, as a result, nginx
worker would crash due to stack overflow whenever such dependency was
introduced.

Found with afl-fuzz.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

1 files changed, 13 insertions, 4 deletions

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
index 6cca2b9a3..51cf65a88 100644
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -2914,11 +2914,14 @@ ngx_http_v2_get_closed_node(ngx_http_v2_connection_t *h2c)
         weight += child->weight;
     }
 
+    parent = node->parent;
+
     for (q = ngx_queue_head(&node->children);
          q != ngx_queue_sentinel(&node->children);
          q = ngx_queue_next(q))
     {
         child = ngx_queue_data(q, ngx_http_v2_node_t, queue);
+        child->parent = parent;
         child->weight = node->weight * child->weight / weight;
 
         if (child->weight == 0) {
@@ -2926,8 +2929,6 @@ ngx_http_v2_get_closed_node(ngx_http_v2_connection_t *h2c)
         }
     }
 
-    parent = node->parent;
-
     if (parent == NGX_HTTP_V2_ROOT) {
         node->rank = 0;
         node->rel_weight = 1.0;
@@ -3940,8 +3941,8 @@ static void
 ngx_http_v2_set_dependency(ngx_http_v2_connection_t *h2c,
     ngx_http_v2_node_t *node, ngx_uint_t depend, ngx_uint_t exclusive)
 {
-    ngx_queue_t         *children;
-    ngx_http_v2_node_t  *parent, *next;
+    ngx_queue_t         *children, *q;
+    ngx_http_v2_node_t  *parent, *child, *next;
 
     parent = depend ? ngx_http_v2_get_node_by_id(h2c, depend, 0) : NULL;
 
@@ -4003,6 +4004,14 @@ ngx_http_v2_set_dependency(ngx_http_v2_connection_t *h2c,
     }
 
     if (exclusive) {
+        for (q = ngx_queue_head(children);
+             q != ngx_queue_sentinel(children);
+             q = ngx_queue_next(q))
+        {
+            child = ngx_queue_data(q, ngx_http_v2_node_t, queue);
+            child->parent = node;
+        }
+
         ngx_queue_add(&node->children, children);
         ngx_queue_init(children);
     }