Currently, Alpha's pci_mmap_resource() does not check
security_locked_down(LOCKDOWN_PCI_ACCESS) before allowing
userspace to mmap PCI BARs.

The generic version has had this check since commit eb627e17727e
("PCI: Lock down BAR access when the kernel is locked down") to
prevent DMA attacks when the kernel is locked down.

Add the same check to Alpha's pci_mmap_resource().

Fixes: eb627e17727e ("PCI: Lock down BAR access when the kernel is locked down")
Tested-by: Magnus Lindholm <linmag7@gmail.com>
Tested-by: Shivaprasad G Bhat <redacted>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Magnus Lindholm <linmag7@gmail.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
---
 arch/alpha/kernel/pci-sysfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/alpha/kernel/pci-sysfs.c b/arch/alpha/kernel/pci-sysfs.c
index 3048758304b5..2324720c3e83 100644
--- a/arch/alpha/kernel/pci-sysfs.c
+++ b/arch/alpha/kernel/pci-sysfs.c

@@ -11,6 +11,7 @@
  */
 
 #include <linux/sched.h>
+#include <linux/security.h>
 #include <linux/stat.h>
 #include <linux/slab.h>
 #include <linux/pci.h>

@@ -71,7 +72,11 @@ static int pci_mmap_resource(struct kobject *kobj,
 	struct resource *res = attr->private;
 	enum pci_mmap_state mmap_type;
 	struct pci_bus_region bar;
-	int i;
+	int i, ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
 
 	for (i = 0; i < PCI_STD_NUM_BARS; i++)
 		if (res == &pdev->resource[i])

-- 
2.54.0