[PATCH 1/2] efi/arm64: fix potential NULL dereference of efi.systab

[Ard Biesheuvel]

We assign efi.systab using efi_lookup_mapped_addr(), and test for !NULL, but
then go on an dereference it anyway.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---
 arch/arm64/kernel/efi.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 56c3327bbf79..e785f93f17cb 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -419,8 +419,11 @@ static int __init arm64_enter_virtual_mode(void)
 	}
 
 	efi.systab = (__force void *)efi_lookup_mapped_addr(efi_system_table);
-	if (efi.systab)
-		set_bit(EFI_SYSTEM_TABLES, &efi.flags);
+	if (!efi.systab) {
+		pr_err("Failed to remap EFI System Table!\n");
+		return -1;
+	}
+	set_bit(EFI_SYSTEM_TABLES, &efi.flags);
 
 	local_irq_save(flags);
 	cpu_switch_mm(idmap_pg_dir, &init_mm);
-- 
1.8.3.2