Re: [PATCH v3] PCI/sysfs: Change read permissions for VPD attributes

[Stephen Hemminger]

On Tue,  3 Dec 2024 14:15:28 +0200
Leon Romanovsky <leon@xxxxxxxxxx> wrote:

> The Vital Product Data (VPD) attribute is not readable by regular
> user without root permissions. Such restriction is not needed at
> all for Mellanox devices, as data presented in that VPD is not
> sensitive and access to the HW is safe and well tested.
> 
> This change changes the permissions of the VPD attribute to be accessible
> for read by all users for Mellanox devices, while write continue to be
> restricted to root only.
> 
> The main use case is to remove need to have root/setuid permissions
> while using monitoring library [1].
> 
> [leonro@vm ~]$ lspci |grep nox
> 00:09.0 Ethernet controller: Mellanox Technologies MT2910 Family [ConnectX-7]
> 
> Before:
> [leonro@vm ~]$ ls -al /sys/bus/pci/devices/0000:00:09.0/vpd
> -rw------- 1 root root 0 Nov 13 12:30 /sys/bus/pci/devices/0000:00:09.0/vpd
> After:
> [leonro@vm ~]$ ls -al /sys/bus/pci/devices/0000:00:09.0/vpd
> -rw-r--r-- 1 root root 0 Nov 13 12:30 /sys/bus/pci/devices/0000:00:09.0/vpd
> 
> [1] https://developer.nvidia.com/management-library-nvml
> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> ---
> Changelog:
> v3:
>  * Used | to change file attributes
>  * Remove WARN_ON
> v2: https://lore.kernel.org/all/61a0fa74461c15edfae76222522fa445c28bec34.1731502431.git.leon@xxxxxxxxxx
>  * Another implementation to make sure that user is presented with
>    correct permissions without need for driver intervention.
> v1: https://lore.kernel.org/all/cover.1731005223.git.leonro@xxxxxxxxxx
>  * Changed implementation from open-read-to-everyone to be opt-in
>  * Removed stable and Fixes tags, as it seems like feature now.
> v0:
> https://lore.kernel.org/all/65791906154e3e5ea12ea49127cf7c707325ca56.1730102428.git.leonro@xxxxxxxxxx/
> ---
>  drivers/pci/vpd.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/pci/vpd.c b/drivers/pci/vpd.c
> index a469bcbc0da7..a7aa54203321 100644
> --- a/drivers/pci/vpd.c
> +++ b/drivers/pci/vpd.c
> @@ -332,6 +332,13 @@ static umode_t vpd_attr_is_visible(struct kobject *kobj,
>  	if (!pdev->vpd.cap)
>  		return 0;
>  
> +	/*
> +	 * Mellanox devices have implementation that allows VPD read by
> +	 * unprivileged users, so just add needed bits to allow read.
> +	 */
> +	if (unlikely(pdev->vendor == PCI_VENDOR_ID_MELLANOX))
> +		return a->attr.mode | 0044;
> +
>  	return a->attr.mode;
>  }
>  

Could this be with other vendor specific quirks instead?

Also, the wording of the comment is awkward. Suggest:
	On Mellanox devices reading VPD is safe for unprivileged users.