Message-ID: <16a26e56-3795-50f8-a32f-d3528696847f@deltatee.com>
Date:   Mon, 6 Feb 2023 11:21:09 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.6.1
Content-Language: en-CA
To:     Chaitanya Kulkarni <chaitanyak@nvidia.com>
Cc:     "oe-kbuild-all@lists.linux.dev" <oe-kbuild-all@lists.linux.dev>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jens Axboe <axboe@kernel.dk>,
        kernel test robot <lkp@intel.com>,
        Christoph Hellwig <hch@lst.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
References: <202302020153.4eL3mwiK-lkp@intel.com>
 <6359dcaa-0817-4819-321c-f786809ff89d@nvidia.com>
From:   Logan Gunthorpe <logang@deltatee.com>
In-Reply-To: <6359dcaa-0817-4819-321c-f786809ff89d@nvidia.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Subject: Re: drivers/pci/p2pdma.c:199:44: sparse: sparse: dereference of
 noderef expression
Precedence: bulk


On 2023-02-06 8:26 a.m., Chaitanya Kulkarni wrote:
> Logan,
> 
>> If you fix the issue, kindly add following tag where applicable
>> | Reported-by: kernel test robot <lkp@intel.com>
>>
>> sparse warnings: (new ones prefixed by >>)
>>>> drivers/pci/p2pdma.c:199:44: sparse: sparse: dereference of noderef expression
>>
>> vim +199 drivers/pci/p2pdma.c
>>
>>     193	
>>     194	static void p2pdma_page_free(struct page *page)
>>     195	{
>>     196		struct pci_p2pdma_pagemap *pgmap = to_p2p_pgmap(page->pgmap);
>>     197		struct percpu_ref *ref;
>>     198	
>>   > 199		gen_pool_free_owner(pgmap->provider->p2pdma->pool,
>>     200				    (uintptr_t)page_to_virt(page), PAGE_SIZE,
>>     201				    (void **)&ref);
>>     202		percpu_ref_put(ref);
>>     203	}
>>     204	
>>
> 
> Did you get a chance to look into this ?

Oh, I didn't notice that email. Wonder why it took this long for sparse
to see that.

Looks like we need to add a rcu_derference_protected() around the p2pdma
dereference there. I can send a patch later this week.

Thanks,

Logan