[PATCH v2] drm/i915: Guard against NULL driver_data in i915_pci_probe()

pci_match_device() can return the dummy pci_device_id_any entry
when a device is force-bound via sysfs driver_override, in which
case ->driver_data is unset (NULL). i915_pci_probe() casts it to
struct intel_device_info * unconditionally and dereferences
intel_info->require_force_probe, causing a NULL-ptr-deref.

Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=db96c5ff032f4292a8dc
Tested-by: [email protected]
Cc: [email protected]
Signed-off-by: Deepanshu Kartikey <[email protected]>
---
v2: Drop Fixes tag, this isn't a regression from a single commit -
    the unconditional dereference of ->driver_data has always assumed
    it points into a MODULE_DEVICE_TABLE()-backed entry, an assumption
    broken by the generic driver_override fallback path, not by any
    i915-specific change. Add Cc: stable instead. (Krzysztof, Jani)
---
 drivers/gpu/drm/i915/i915_pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
index 82415af47d54..2f03f95945f1 100644
--- a/drivers/gpu/drm/i915/i915_pci.c
+++ b/drivers/gpu/drm/i915/i915_pci.c
@@ -958,6 +958,9 @@ static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		(struct intel_device_info *) ent->driver_data;
 	int err;
 
+	if (!intel_info)
+		return -ENODEV;
+
 	if (intel_info->require_force_probe && !id_forced(pdev->device)) {
 		dev_info(&pdev->dev,
 			 "Your graphics device %04x is not properly supported by i915 in this\n"
-- 
2.43.0