of: Fix NULL dereference in unflatten_and_copy()

Check whether initial_boot_params is NULL before dereferencing it in
unflatten_and_copy_device_tree() for the case where no device tree is
available but the arch can still boot to a minimal usable system without
it. In this case also log a warning for when the kernel log buffer is
obtainable.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 2fa024b97c43..758b4f8b30b7 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -922,8 +922,16 @@ void __init unflatten_device_tree(void)
  */
 void __init unflatten_and_copy_device_tree(void)
 {
-        int size = __be32_to_cpu(initial_boot_params->totalsize);
-        void *dt = early_init_dt_alloc_memory_arch(size,
+        int size;
+        void *dt;
+
+        if (!initial_boot_params) {
+                pr_warn("No valid device tree found, continuing without\n");
+                return;
+        }
+
+        size = __be32_to_cpu(initial_boot_params->totalsize);
+        dt = early_init_dt_alloc_memory_arch(size,
                 __alignof__(struct boot_param_header));
 
         if (dt) {