linux-kernel - Re: [PATCH 3/6] pci/p2pdma: Fix the gen_pool_add

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Message-ID: <20190329172406.GE24180@google.com>
Date:   Fri, 29 Mar 2019 12:24:06 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     akpm@...ux-foundation.org, Logan Gunthorpe <logang@...tatee.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Christoph Hellwig <hch@....de>, linux-mm@...ck.org,
        linux-pci@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] pci/p2pdma: Fix the gen_pool_add_virt() failure path

On Fri, Mar 29, 2019 at 08:27:39AM -0700, Dan Williams wrote:
> The pci_p2pdma_add_resource() implementation immediately frees the pgmap
> if gen_pool_add_virt() fails. However, that means that when @dev
> triggers a devres release devm_memremap_pages_release() will crash
> trying to access the freed @pgmap.
> 
> Use the new devm_memunmap_pages() to manually free the mapping in the
> error path.
> 
> Fixes: 52916982af48 ("PCI/P2PDMA: Support peer-to-peer memory")
> Cc: Logan Gunthorpe <logang@...tatee.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Christoph Hellwig <hch@....de>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Especially if you run "git log --oneline drivers/pci/p2pdma.c" and make
yours match :),

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/pci/p2pdma.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index c52298d76e64..595a534bd749 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -208,13 +208,15 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
>  			pci_bus_address(pdev, bar) + offset,
>  			resource_size(&pgmap->res), dev_to_node(&pdev->dev));
>  	if (error)
> -		goto pgmap_free;
> +		goto pages_free;
>  
>  	pci_info(pdev, "added peer-to-peer DMA memory %pR\n",
>  		 &pgmap->res);
>  
>  	return 0;
>  
> +pages_free:
> +	devm_memunmap_pages(&pdev->dev, pgmap);
>  pgmap_free:
>  	devm_kfree(&pdev->dev, pgmap);
>  	return error;
>