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

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Date:   Fri, 2 Dec 2022 09:39:45 +0800
From:   "Ziyang Xuan (William)" <william.xuanziyang@...wei.com>
To:     Paolo Abeni <pabeni@...hat.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.

Yes, you are right. I did pay much attention to sq->sqb_ptrs[],
and omitted the for loop condition.

Thank you!

> 
> Cheers,
> 
> Paolo
>>  	}
> 
> 
> .
>