Re: [PATCH] libertas: Fix a double free in if_spi_c2h_data()

[Dan Williams]

On Wed, 2019-06-26 at 13:09 +0300, Dan Carpenter wrote:
> The lbs_process_rxed_packet() frees the skb.  It didn't originally,
> but
> we fixed it in commit f54930f36311 ("libertas: don't leak skb on
> receive
> error").
> 
> Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>
> ---
>  drivers/net/wireless/marvell/libertas/if_spi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/marvell/libertas/if_spi.c
> b/drivers/net/wireless/marvell/libertas/if_spi.c
> index 27067e79e83f..e38f02d1f2e4 100644
> --- a/drivers/net/wireless/marvell/libertas/if_spi.c
> +++ b/drivers/net/wireless/marvell/libertas/if_spi.c
> @@ -772,7 +772,7 @@ static int if_spi_c2h_data(struct if_spi_card
> *card)
>       /* pass the SKB to libertas */
>       err = lbs_process_rxed_packet(card->priv, skb);
>       if (err)
> -             goto free_skb;
> +             goto out;  /* lbs_process_rxed_packet() frees skb */
>  
>       /* success */
>       goto out;

It can be further simplified (not compile tested yet):

diff --git a/drivers/net/wireless/marvell/libertas/if_spi.c 
b/drivers/net/wireless/marvell/libertas/if_spi.c
index 27067e79e83fe..072da89c4986f 100644
--- a/drivers/net/wireless/marvell/libertas/if_spi.c
+++ b/drivers/net/wireless/marvell/libertas/if_spi.c
@@ -766,19 +766,15 @@ static int if_spi_c2h_data(struct if_spi_card *card)
 
        /* Read the data from the WLAN module into our skb... */
        err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, 4));
-       if (err)
-               goto free_skb;
+       if (err) {
+               dev_kfree_skb(skb);
+               goto out
+       }
 
        /* pass the SKB to libertas */
        err = lbs_process_rxed_packet(card->priv, skb);
-       if (err)
-               goto free_skb;
+       /* lbs_process_rxed_packet() consumes the skb */
 
-       /* success */
-       goto out;
-
-free_skb:
-       dev_kfree_skb(skb);
 out:
        if (err)
                netdev_err(priv->dev, "%s: err=%d\n", __func__, err);