Update Linux to v5.4.148

Sourced from [1]

[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.4.148.tar.gz

Change-Id: Ib3d26c5ba9b022e2e03533005c4fed4d7c30b61b
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index af64519..da3cc3a 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -316,7 +316,7 @@
 		 */
 		mutex_lock(&task->mm->context.lock);
 		ldt = task->mm->context.ldt;
-		if (unlikely(idx >= ldt->nr_entries))
+		if (unlikely(!ldt || idx >= ldt->nr_entries))
 			base = 0;
 		else
 			base = get_desc_base(ldt->entries + idx);