linux-kernel - Re: [PATCH v2 1/1] Guard pci_create_sysfs_dev

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Date:   Thu, 16 Mar 2023 10:23:54 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Alexander Stein <alexander.stein@...tq-group.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     Korneliusz Osmenda <korneliuszo@...il.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] Guard pci_create_sysfs_dev_files with atomic value



On 16.03.23 10:15, Alexander Stein wrote:
> From: Korneliusz Osmenda <korneliuszo@...il.com>
> 
> On Gateworks Ventana there is a number of PCI devices and:
>    - imx6_pcie_probe takes longer than start of late init
>    - pci_sysfs_init sets up flag sysfs_initialized
>    - pci_sysfs_init initializes already found devices
>    - imx6_pcie_probe tries to reinitialize device
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=215515
> 
> Signed-off-by: Korneliusz Osmenda <korneliuszo@...il.com>
> Signed-off-by: Alexander Stein <alexander.stein@...tq-group.com>
> ---
>   drivers/pci/pci-sysfs.c | 6 ++++++
>   include/linux/pci.h     | 2 ++
>   2 files changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index dd0d9d9bc509..998e44716b6f 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1497,6 +1497,9 @@ int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev)
>   	if (!sysfs_initialized)
>   		return -EACCES;
>   
> +	if (atomic_cmpxchg(&pdev->sysfs_init_cnt, 0, 1) == 1)
> +		return 0;		/* already added */
> +
>   	return pci_create_resource_files(pdev);

This is very likely a bug. You are returning an error in the error
case. Yet the flag stays. And simply resetting it in the error case
would be a race. There is something fishy in that design.

	Regards
		Oliver