netdev - Re: [PATCH net 2/2] octeontx2-pf: Fix a potential double free in otx2_sq_free

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Date:   Tue, 29 Nov 2022 13:03:56 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Ziyang Xuan <william.xuanziyang@...wei.com>, sgoutham@...vell.com,
        gakula@...vell.com, sbhatta@...vell.com, hkelam@...vell.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 2/2] octeontx2-pf: Fix a potential double free in
 otx2_sq_free_sqbs()

Hello,

On Fri, 2022-11-25 at 15:45 +0800, Ziyang Xuan wrote:
> otx2_sq_free_sqbs() will be called twice when goto "err_free_nix_queues"
> label in otx2_init_hw_resources(). The first calling is within
> otx2_free_sq_res() at "err_free_nix_queues" label, and the second calling
> is at later "err_free_sq_ptrs" label.
> 
> In otx2_sq_free_sqbs(), If sq->sqb_ptrs[i] is not 0, the memory page it
> points to will be freed, and sq->sqb_ptrs[i] do not be assigned 0 after
> memory page be freed. If otx2_sq_free_sqbs() is called twice, the memory
> page pointed by sq->sqb_ptrs[i] will be freeed twice. To fix the bug,
> assign 0 to sq->sqb_ptrs[i] after memory page be freed.
> 
> Fixes: caa2da34fd25 ("octeontx2-pf: Initialize and config queues")
> Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.com>
> ---
>  drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> index 9e10e7471b88..5a25fe51d102 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> @@ -1146,6 +1146,7 @@ void otx2_sq_free_sqbs(struct otx2_nic *pfvf)
>  					     DMA_FROM_DEVICE,
>  					     DMA_ATTR_SKIP_CPU_SYNC);
>  			put_page(virt_to_page(phys_to_virt(pa)));
> +			sq->sqb_ptrs[sqb] = 0;

The above looks not needed...
>  		}
>  		sq->sqb_count = 0;

... as this will prevent the next invocation of otx2_sq_free_sqbs()
from traversing and freeing any sq->sqb_ptrs[] element.

Cheers,

Paolo
>  	}