linux-kernel - Re: drivers/pci/p2pdma.c:199:44: sparse: sparse: dereference of noderef expression

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Date:   Mon, 6 Feb 2023 11:21:09 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Chaitanya Kulkarni <chaitanyak@...dia.com>
Cc:     "oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>,
        kernel test robot <lkp@...el.com>,
        Christoph Hellwig <hch@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: drivers/pci/p2pdma.c:199:44: sparse: sparse: dereference of
 noderef expression



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@...el.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