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Message-ID: <1c639919-342a-cccc-1cad-772455b72656@embeddedor.com>
Date: Fri, 22 Sep 2023 18:59:23 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Kees Cook <keescook@...omium.org>,
Mirko Lindner <mlindner@...vell.com>
Cc: 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>,
Alexander Lobakin <aleksander.lobakin@...el.com>,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] sky2: Make sure there is at least one frag_addr
available
On 9/22/23 10:50, Kees Cook wrote:
> In the pathological case of building sky2 with 16k PAGE_SIZE, the
> frag_addr[] array would never be used, so the original code was correct
> that size should be 0. But the compiler now gets upset with 0 size arrays
> in places where it hasn't eliminated the code that might access such an
> array (it can't figure out that in this case an rx skb with fragments
> would never be created). To keep the compiler happy, 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/
> Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Thanks
--
Gustavo
> ---
> v2 - improve commit message, add Ack
> v1 - https://lore.kernel.org/netdev/20230920202509.never.299-kees@kernel.org/
> ---
> 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 {
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