linux-kernel - Re: [PATCH] sky2: Make sure there is at least one frag

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Message-ID: <d7462ae5-c971-452f-49d7-855f60c850d3@intel.com>
Date:   Thu, 21 Sep 2023 16:14:30 +0200
From:   Alexander Lobakin <aleksander.lobakin@...el.com>
To:     Kees Cook <keescook@...omium.org>
CC:     Mirko Lindner <mlindner@...vell.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Eric Dumazet" <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        kernel test robot <lkp@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH] sky2: Make sure there is at least one frag_addr available

From: Kees Cook <keescook@...omium.org>
Date: Wed, 20 Sep 2023 13:25:13 -0700

> In the likely pathological case of building sky2 with 16k PAGE_SIZE,
> make sure there is at least 1 frag_addr in struct rx_ring_info:
> 
>    In file included from include/linux/skbuff.h:28,
>                     from include/net/net_namespace.h:43,
>                     from include/linux/netdevice.h:38,
>                     from drivers/net/ethernet/marvell/sky2.c:18:
>    drivers/net/ethernet/marvell/sky2.c: In function 'sky2_rx_unmap_skb':
>    include/linux/dma-mapping.h:416:36: warning: array subscript i is outside array bounds of 'dma_addr_t[0]' {aka 'long long unsigned int[]'} [-Warray-bounds=]
>      416 | #define dma_unmap_page(d, a, s, r) dma_unmap_page_attrs(d, a, s, r, 0)
>          |                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    drivers/net/ethernet/marvell/sky2.c:1257:17: note: in expansion of macro 'dma_unmap_page'
>     1257 |                 dma_unmap_page(&pdev->dev, re->frag_addr[i],
>          |                 ^~~~~~~~~~~~~~
>    In file included from drivers/net/ethernet/marvell/sky2.c:41:
>    drivers/net/ethernet/marvell/sky2.h:2198:25: note: while referencing 'frag_addr'
>     2198 |         dma_addr_t      frag_addr[ETH_JUMBO_MTU >> PAGE_SHIFT];
>          |                         ^~~~~~~~~
> 
> With CONFIG_PAGE_SIZE_16KB=y, PAGE_SHIFT == 14, so:
> 
>   #define ETH_JUMBO_MTU   9000
> 
> causes "ETH_JUMBO_MTU >> PAGE_SHIFT" to be 0. Use "?: 1" to solve this build warning.
> 
> Cc: Mirko Lindner <mlindner@...vell.com>
> Cc: Stephen Hemminger <stephen@...workplumber.org>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: netdev@...r.kernel.org
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202309191958.UBw1cjXk-lkp@intel.com/
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>

That "nobody uses this HW on non-x86 systems, why bother" is fun each time.

> ---
>  drivers/net/ethernet/marvell/sky2.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/marvell/sky2.h b/drivers/net/ethernet/marvell/sky2.h
> index ddec1627f1a7..8d0bacf4e49c 100644
> --- a/drivers/net/ethernet/marvell/sky2.h
> +++ b/drivers/net/ethernet/marvell/sky2.h
> @@ -2195,7 +2195,7 @@ struct rx_ring_info {
>  	struct sk_buff	*skb;
>  	dma_addr_t	data_addr;
>  	DEFINE_DMA_UNMAP_LEN(data_size);
> -	dma_addr_t	frag_addr[ETH_JUMBO_MTU >> PAGE_SHIFT];
> +	dma_addr_t	frag_addr[ETH_JUMBO_MTU >> PAGE_SHIFT ?: 1];
>  };
>  
>  enum flow_control {

Thanks,
Olek