net: stmmac: clean up impossible condition

This code works but it has a static checker warning:

    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:1687 init_dma_rx_desc_rings()
    warn: always true condition '(queue >= 0) => (0-u32max >= 0)'

Obviously, it makes no sense to check if an unsigned int is >= 0.  What
prevents this code from being a forever loop is that later there is a
separate check for if (queue == 0).

The "queue" variable is less than MTL_MAX_RX_QUEUES (8) so it can easily
fit in an int type.  Any larger value for "queue" would lead to an array
overflow when we assign "rx_q = &priv->rx_queue[queue]".

Fixes: de0b90e52a11 ("net: stmmac: rearrange RX and TX desc init into per-queue basis")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20220316083744.GB30941@kili
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index c1bfd89..4a4b365 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1668,7 +1668,7 @@ static int init_dma_rx_desc_rings(struct net_device *dev, gfp_t flags)
 {
        struct stmmac_priv *priv = netdev_priv(dev);
        u32 rx_count = priv->plat->rx_queues_to_use;
-       u32 queue;
+       int queue;
        int ret;
 
        /* RX INITIALIZATION */
@@ -1695,9 +1695,6 @@ err_init_rx_buffers:
                rx_q->buf_alloc_num = 0;
                rx_q->xsk_pool = NULL;
 
-               if (queue == 0)
-                       break;
-
                queue--;
        }