drm/xe/configfs: Enforce canonical device names

While we expect config directory names to match PCI device name,
currently we are only scanning provided names for domain, bus,
device and function numbers, without checking their format.
This would pass slightly broken entries like:

  /sys/kernel/config/xe/
  ├── 0000:00:02.0000000000000
  │   └── ...
  ├── 0000:00:02.0x
  │   └── ...
  ├──  0: 0: 2. 0
  │   └── ...
  └── 0:0:2.0
      └── ...

To avoid such mistakes, check if the name provided exactly matches
the canonical PCI device address format, which we recreated from
the parsed BDF data. Also simplify scanf format as it can't really
catch all formatting errors.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250722141059.30707-3-michal.wajdeczko@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

diff --git a/drivers/gpu/drm/xe/xe_configfs.c b/drivers/gpu/drm/xe/xe_configfs.c
index e9b46a2d00195a69c7cb616930232c853392426b..f5ce48a0adc8bd1e7a6e947fc811d342d8196fcc 100644 (file)
--- a/drivers/gpu/drm/xe/xe_configfs.c
+++ b/drivers/gpu/drm/xe/xe_configfs.c
@@ -259,12 +259,19 @@ static struct config_group *xe_config_make_device_group(struct config_group *gro
        unsigned int domain, bus, slot, function;
        struct xe_config_device *dev;
        struct pci_dev *pdev;
+       char canonical[16];
        int ret;
 
-       ret = sscanf(name, "%04x:%02x:%02x.%x", &domain, &bus, &slot, &function);
+       ret = sscanf(name, "%x:%x:%x.%x", &domain, &bus, &slot, &function);
        if (ret != 4)
                return ERR_PTR(-EINVAL);
 
+       ret = scnprintf(canonical, sizeof(canonical), "%04x:%02x:%02x.%d", domain, bus,
+                       PCI_SLOT(PCI_DEVFN(slot, function)),
+                       PCI_FUNC(PCI_DEVFN(slot, function)));
+       if (ret != 12 || strcmp(name, canonical))
+               return ERR_PTR(-EINVAL);
+
        pdev = pci_get_domain_bus_and_slot(domain, bus, PCI_DEVFN(slot, function));
        if (!pdev)
                return ERR_PTR(-ENODEV);