[PATCH 2/5] drm/xe/configfs: Enforce canonical device names

[Michal Wajdeczko]

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 at intel.com>
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
---
 drivers/gpu/drm/xe/xe_configfs.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_configfs.c b/drivers/gpu/drm/xe/xe_configfs.c
index e9b46a2d0019..90b4fe92a611 100644
--- 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.%d", &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);
-- 
2.47.1