net: stmmac: Avoid VLA usage

In the quest to remove all stack VLAs from the kernel[1], this switches
the "status" stack buffer to use the existing small (8) upper bound on
how many queues can be checked for DMA, and adds a sanity-check just to
make sure it doesn't operate under pathological conditions.

[1] http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 0135fd3..b935478 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2022,7 +2022,11 @@ static void stmmac_dma_interrupt(struct stmmac_priv *priv)
                                tx_channel_count : rx_channel_count;
        u32 chan;
        bool poll_scheduled = false;
-       int status[channels_to_check];
+       int status[max_t(u32, MTL_MAX_TX_QUEUES, MTL_MAX_RX_QUEUES)];
+
+       /* Make sure we never check beyond our status buffer. */
+       if (WARN_ON_ONCE(channels_to_check > ARRAY_SIZE(status)))
+               channels_to_check = ARRAY_SIZE(status);
 
        /* Each DMA channel can be used for rx and tx simultaneously, yet
         * napi_struct is embedded in struct stmmac_rx_queue rather than in a