Re: [PATCH] PCI/sysfs: Fix double free in error path

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Bjorn,

On Fri, Oct 07, 2022 at 08:56:18AM +0200, Sascha Hauer wrote:
> When pci_create_attr() fails then pci_remove_resource_files() is called
> which will iterate over the res_attr[_wc] arrays and frees every non
> NULL entry. To avoid a double free here we have to set the failed entry
> to NULL in pci_create_attr() when freeing it.
> 
> Fixes: b562ec8f74e4 ("PCI: Don't leak memory if sysfs_create_bin_file() fails")
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: <stable@vger.kernel.org>
> ---
>  drivers/pci/pci-sysfs.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)

Any input to this one? There's this long unfixed race condition
described here:

https://patchwork.kernel.org/project/linux-pci/patch/20200716110423.xtfyb3n6tn5ixedh@pali/#23547255

And this patch at least prevents my system from crashing when this race
condition occurs.

Sascha

> 
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index fc804e08e3cb5..a07381d46ddae 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1196,8 +1196,13 @@ static int pci_create_attr(struct pci_dev *pdev, int num, int write_combine)
>  	res_attr->size = pci_resource_len(pdev, num);
>  	res_attr->private = (void *)(unsigned long)num;
>  	retval = sysfs_create_bin_file(&pdev->dev.kobj, res_attr);
> -	if (retval)
> +	if (retval) {
> +		if (write_combine)
> +			pdev->res_attr_wc[num] = NULL;
> +		else
> +			pdev->res_attr[num] = NULL;
>  		kfree(res_attr);
> +	}
>  
>  	return retval;
>  }
> -- 
> 2.30.2
> 
> 

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