[PATCH v5 net] ps3/gelic: Fix SKB allocation

[PATCH v5 net] ps3/gelic: Fix SKB allocation

[Geoff Levand]

Commit 3ce4f9c3fbb3 ("net/ps3_gelic_net: Add gelic_descr structures") of
6.8-rc1 had a copy-and-paste error where the pointer that holds the
allocated SKB (struct gelic_descr.skb)  was set to NULL after the SKB was
allocated. This resulted in a kernel panic when the SKB pointer was
accessed.

This fix moves the initialization of the gelic_descr to before the SKB
is allocated.

Reported-by: sambat goson <sombat3960@gmail.com>
Fixes: 3ce4f9c3fbb3 ("net/ps3_gelic_net: Add gelic_descr structures")
Signed-off-by: Geoff Levand <geoff@infradead.org>

diff --git a/drivers/net/ethernet/toshiba/ps3_gelic_net.c b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
index d5b75af163d3..28116891d2ce 100644
--- a/drivers/net/ethernet/toshiba/ps3_gelic_net.c
+++ b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
@@ -384,11 +384,6 @@ static int gelic_descr_prepare_rx(struct gelic_card *card,
 	if (gelic_descr_get_status(descr) !=  GELIC_DESCR_DMA_NOT_IN_USE)
 		dev_info(ctodev(card), "%s: ERROR status\n", __func__);
 
-	descr->skb = netdev_alloc_skb(*card->netdev, rx_skb_size);
-	if (!descr->skb) {
-		descr->hw_regs.payload.dev_addr = 0; /* tell DMAC don't touch memory */
-		return -ENOMEM;
-	}
 	descr->hw_regs.dmac_cmd_status = 0;
 	descr->hw_regs.result_size = 0;
 	descr->hw_regs.valid_size = 0;
@@ -397,6 +392,12 @@ static int gelic_descr_prepare_rx(struct gelic_card *card,
 	descr->hw_regs.payload.size = 0;
 	descr->skb = NULL;
 
+	descr->skb = netdev_alloc_skb(*card->netdev, rx_skb_size);
+	if (!descr->skb) {
+		descr->hw_regs.payload.dev_addr = 0; /* tell DMAC don't touch memory */
+		return -ENOMEM;
+	}
+
 	offset = ((unsigned long)descr->skb->data) &
 		(GELIC_NET_RXBUF_ALIGN - 1);
 	if (offset)

Re: [PATCH v5 net] ps3/gelic: Fix SKB allocation

[Christophe Leroy]

Le 19/02/2024 à 10:12, Geoff Levand a écrit :
> Commit 3ce4f9c3fbb3 ("net/ps3_gelic_net: Add gelic_descr structures") of
> 6.8-rc1 had a copy-and-paste error where the pointer that holds the
> allocated SKB (struct gelic_descr.skb)  was set to NULL after the SKB was
> allocated. This resulted in a kernel panic when the SKB pointer was
> accessed.
> 
> This fix moves the initialization of the gelic_descr to before the SKB
> is allocated.
> 
> Reported-by: sambat goson <sombat3960@gmail.com>
> Fixes: 3ce4f9c3fbb3 ("net/ps3_gelic_net: Add gelic_descr structures")
> Signed-off-by: Geoff Levand <geoff@infradead.org>
> 
> diff --git a/drivers/net/ethernet/toshiba/ps3_gelic_net.c b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
> index d5b75af163d3..28116891d2ce 100644
> --- a/drivers/net/ethernet/toshiba/ps3_gelic_net.c
> +++ b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
> @@ -384,11 +384,6 @@ static int gelic_descr_prepare_rx(struct gelic_card *card,
>   	if (gelic_descr_get_status(descr) !=  GELIC_DESCR_DMA_NOT_IN_USE)
>   		dev_info(ctodev(card), "%s: ERROR status\n", __func__);
>   
> -	descr->skb = netdev_alloc_skb(*card->netdev, rx_skb_size);
> -	if (!descr->skb) {
> -		descr->hw_regs.payload.dev_addr = 0; /* tell DMAC don't touch memory */
> -		return -ENOMEM;
> -	}
>   	descr->hw_regs.dmac_cmd_status = 0;
>   	descr->hw_regs.result_size = 0;
>   	descr->hw_regs.valid_size = 0;
> @@ -397,6 +392,12 @@ static int gelic_descr_prepare_rx(struct gelic_card *card,
>   	descr->hw_regs.payload.size = 0;
>   	descr->skb = NULL;

You are unconditionaly re-assigning value to descr->skb below, so above 
line is useless and should be removed.

>   
> +	descr->skb = netdev_alloc_skb(*card->netdev, rx_skb_size);
> +	if (!descr->skb) {
> +		descr->hw_regs.payload.dev_addr = 0; /* tell DMAC don't touch memory */
> +		return -ENOMEM;
> +	}
> +

Is this code move needed at all ?

At the end, isn't it enough to just drop the line descr->skb = NULL; ?

Christophe

>   	offset = ((unsigned long)descr->skb->data) &
>   		(GELIC_NET_RXBUF_ALIGN - 1);
>   	if (offset)