linux-kernel - Re: [PATCH 4.19 19/38] sfc: falcon: Check null pointer of rx_queue->page

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Message-ID: <20211229112120.GC25195@amd>
Date:   Wed, 29 Dec 2021 12:21:20 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jiasheng Jiang <jiasheng@...as.ac.cn>,
        Martin Habets <habetsm.xilinx@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 19/38] sfc: falcon: Check null pointer of
 rx_queue->page_ring

Hi!

> From: Jiasheng Jiang <jiasheng@...as.ac.cn>
> 
> [ Upstream commit 9b8bdd1eb5890aeeab7391dddcf8bd51f7b07216 ]
> 
> Because of the possible failure of the kcalloc, it should be better to
> set rx_queue->page_ptr_mask to 0 when it happens in order to maintain
> the consistency.

Again this is confusing/wrong, or at least not a complete fix...

> +++ b/drivers/net/ethernet/sfc/falcon/rx.c
> @@ -732,7 +732,10 @@ static void ef4_init_rx_recycle_ring(struct ef4_nic *efx,
>  					    efx->rx_bufs_per_page);
>  	rx_queue->page_ring = kcalloc(page_ring_size,
>  				      sizeof(*rx_queue->page_ring), GFP_KERNEL);
> -	rx_queue->page_ptr_mask = page_ring_size - 1;
> +	if (!rx_queue->page_ring)
> +		rx_queue->page_ptr_mask = 0;
> +	else
> +		rx_queue->page_ptr_mask = page_ring_size - 1;
>  }
>  

...as we have 

        index = rx_queue->page_remove & rx_queue->page_ptr_mask;
	page = rx_queue->page_ring[index];
		
in ef4_reuse_page, and similar problems in other places, including

        for (i = 0; i <= rx_queue->page_ptr_mask; i++) {
                struct page *page = rx_queue->page_ring[i];

. Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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