[PATCH] virtio-net: Avoid indirection_table_mask overflow

[Akihiko Odaki <akihiko.odaki@daynix.com>]

We computes indirections_len by adding 1 to indirection_table_mask, but
it may overflow indirection_table_mask is UINT16_MAX. Check if
indirection_table_mask is small enough before adding 1.

Fixes: 590790297c0d ("virtio-net: implement RSS configuration command")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 hw/net/virtio-net.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 8f3097270869..625852a590ea 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1400,17 +1400,17 @@ static uint16_t virtio_net_handle_rss(VirtIONet *n,
     n->rss_data.hash_types = virtio_ldl_p(vdev, &cfg.hash_types);
     n->rss_data.indirections_len =
         virtio_lduw_p(vdev, &cfg.indirection_table_mask);
-    n->rss_data.indirections_len++;
     if (!do_rss) {
-        n->rss_data.indirections_len = 1;
+        n->rss_data.indirections_len = 0;
     }
-    if (!is_power_of_2(n->rss_data.indirections_len)) {
-        err_msg = "Invalid size of indirection table";
+    if (n->rss_data.indirections_len >= VIRTIO_NET_RSS_MAX_TABLE_LEN) {
+        err_msg = "Too large indirection table";
         err_value = n->rss_data.indirections_len;
         goto error;
     }
-    if (n->rss_data.indirections_len > VIRTIO_NET_RSS_MAX_TABLE_LEN) {
-        err_msg = "Too large indirection table";
+    n->rss_data.indirections_len++;
+    if (!is_power_of_2(n->rss_data.indirections_len)) {
+        err_msg = "Invalid size of indirection table";
         err_value = n->rss_data.indirections_len;
         goto error;
     }

---
base-commit: 31669121a01a14732f57c49400bc239cf9fd505f
change-id: 20241008-mask-478ed6fe5365

Best regards,
-- 
Akihiko Odaki <akihiko.odaki@daynix.com>