On 2024-11-07 20:56:56+0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@xxxxxxxxxx>
>
> The Vital Product Data (VPD) attribute is not readable by regular
> user without root permissions. Such restriction is not really needed
> for many devices in the world, as data presented in that VPD is not
> sensitive and access to the HW is safe and tested.
>
> This change aligns the permissions of the VPD attribute to be accessible
> for read by all users, while write being restricted to root only.
>
> For the driver, there is a need to opt-in in order to allow this
> functionality.
>
> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> ---
> drivers/pci/vpd.c | 9 ++++++++-
> include/linux/pci.h | 7 ++++++-
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/vpd.c b/drivers/pci/vpd.c
> index e4300f5f304f..7c70930abaa0 100644
> --- a/drivers/pci/vpd.c
> +++ b/drivers/pci/vpd.c
> @@ -156,6 +156,7 @@ static ssize_t pci_vpd_read(struct pci_dev *dev, loff_t pos, size_t count,
> void *arg, bool check_size)
> {
> struct pci_vpd *vpd = &dev->vpd;
> + struct pci_driver *drv;
> unsigned int max_len;
> int ret = 0;
> loff_t end = pos + count;
> @@ -167,6 +168,12 @@ static ssize_t pci_vpd_read(struct pci_dev *dev, loff_t pos, size_t count,
> if (pos < 0)
> return -EINVAL;
>
> + if (!capable(CAP_SYS_ADMIN)) {
> + drv = to_pci_driver(dev->dev.driver);
> + if (!drv || !drv->downgrade_vpd_read)
> + return -EPERM;
> + }
If you move the check into vpd_attr_is_visible() then the sysfs core
will enforce the permissions and it's obvious for the user if they can
or can't read/write the file.
> +
> max_len = check_size ? vpd->len : PCI_VPD_MAX_SIZE;
>
> if (pos >= max_len)
> @@ -317,7 +324,7 @@ static ssize_t vpd_write(struct file *filp, struct kobject *kobj,
>
> return ret;
> }
> -static BIN_ATTR(vpd, 0600, vpd_read, vpd_write, 0);
> +static BIN_ATTR_RW(vpd, 0);
>
> static struct bin_attribute *vpd_attrs[] = {
> &bin_attr_vpd,
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 573b4c4c2be6..b8fed74e742e 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -943,6 +943,10 @@ struct module;
> * how to manage the DMA themselves and set this flag so that
> * the IOMMU layer will allow them to setup and manage their
> * own I/O address space.
> + * @downgrade_vpd_read: Device doesn't require root permissions from the users
> + * to read VPD information. The driver doesn't expose any sensitive
> + * information through that interface and safe to be accessed by
> + * unprivileged users.
> */
> struct pci_driver {
> const char *name;
> @@ -960,7 +964,8 @@ struct pci_driver {
> const struct attribute_group **dev_groups;
> struct device_driver driver;
> struct pci_dynids dynids;
> - bool driver_managed_dma;
> + bool driver_managed_dma : 1;
> + bool downgrade_vpd_read : 1;
> };
>
> #define to_pci_driver(__drv) \
> --
> 2.47.0
>
