net: shaper: flip the polarity of the valid flag

The usual way of inserting entries which are not yet fully ready
into XArray is to have a VALID flag. The shaper code has a NOT_VALID
flag. Since XArray code does not let us create entries with marks
already set - the creation of entries is currently not atomic.

Flip the polarity of the VALID flag. This closes the tiny race
in net_shaper_pre_insert() of entries being created without
the NOT_VALID flag.

Fixes: 93954b40f6a4 ("net-shapers: implement NL set and delete operations")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20260510192904.3987113-2-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/shaper/shaper.c b/net/shaper/shaper.c
index 1069fa4eb9f606be210245253b8f3ff2ba796f0f..d2b8f1f951b1964522d502e9504be2d0e57cef06 100644 (file)
--- a/net/shaper/shaper.c
+++ b/net/shaper/shaper.c
@@ -275,11 +275,13 @@ static void net_shaper_default_parent(const struct net_shaper_handle *handle,
        parent->id = 0;
 }
 
-/*
- * MARK_0 is already in use due to XA_FLAGS_ALLOC, can't reuse such flag as
- * it's cleared by xa_store().
+/* MARK_0 is already in use due to XA_FLAGS_ALLOC. The VALID mark is set on
+ * an entry only after the device-side configuration has completed
+ * successfully (see net_shaper_commit()). Lookups and dumps must filter on
+ * this mark to avoid exposing tentative entries inserted by
+ * net_shaper_pre_insert() while the driver call is still in flight.
  */
-#define NET_SHAPER_NOT_VALID XA_MARK_1
+#define NET_SHAPER_VALID       XA_MARK_1
 
 static struct net_shaper *
 net_shaper_lookup(struct net_shaper_binding *binding,
@@ -289,8 +291,8 @@ net_shaper_lookup(struct net_shaper_binding *binding,
        struct net_shaper_hierarchy *hierarchy;
 
        hierarchy = net_shaper_hierarchy_rcu(binding);
-       if (!hierarchy || xa_get_mark(&hierarchy->shapers, index,
-                                     NET_SHAPER_NOT_VALID))
+       if (!hierarchy || !xa_get_mark(&hierarchy->shapers, index,
+                                      NET_SHAPER_VALID))
                return NULL;
 
        return xa_load(&hierarchy->shapers, index);
@@ -370,13 +372,10 @@ static int net_shaper_pre_insert(struct net_shaper_binding *binding,
                goto free_id;
        }
 
-       /* Mark 'tentative' shaper inside the hierarchy container.
-        * xa_set_mark is a no-op if the previous store fails.
+       /* Insert as 'tentative' (no VALID mark). The mark will be set by
+        * net_shaper_commit() once the driver-side configuration succeeds.
         */
-       xa_lock(&hierarchy->shapers);
-       prev = __xa_store(&hierarchy->shapers, index, cur, GFP_KERNEL);
-       __xa_set_mark(&hierarchy->shapers, index, NET_SHAPER_NOT_VALID);
-       xa_unlock(&hierarchy->shapers);
+       prev = xa_store(&hierarchy->shapers, index, cur, GFP_KERNEL);
        if (xa_err(prev)) {
                NL_SET_ERR_MSG(extack, "Can't insert shaper into device store");
                kfree_rcu(cur, rcu);
@@ -413,8 +412,7 @@ static void net_shaper_commit(struct net_shaper_binding *binding,
                /* Successful update: drop the tentative mark
                 * and update the hierarchy container.
                 */
-               __xa_clear_mark(&hierarchy->shapers, index,
-                               NET_SHAPER_NOT_VALID);
+               __xa_set_mark(&hierarchy->shapers, index, NET_SHAPER_VALID);
                *cur = shapers[i];
        }
        xa_unlock(&hierarchy->shapers);
@@ -431,8 +429,9 @@ static void net_shaper_rollback(struct net_shaper_binding *binding)
                return;
 
        xa_lock(&hierarchy->shapers);
-       xa_for_each_marked(&hierarchy->shapers, index, cur,
-                          NET_SHAPER_NOT_VALID) {
+       xa_for_each(&hierarchy->shapers, index, cur) {
+               if (xa_get_mark(&hierarchy->shapers, index, NET_SHAPER_VALID))
+                       continue;
                __xa_erase(&hierarchy->shapers, index);
                kfree(cur);
        }
@@ -836,7 +835,8 @@ int net_shaper_nl_get_dumpit(struct sk_buff *skb,
                goto out_unlock;
 
        for (; (shaper = xa_find(&hierarchy->shapers, &ctx->start_index,
-                                U32_MAX, XA_PRESENT)); ctx->start_index++) {
+                                U32_MAX, NET_SHAPER_VALID));
+            ctx->start_index++) {
                ret = net_shaper_fill_one(skb, binding, shaper, info);
                if (ret)
                        break;