x86/efi: Fix dummy variable buffer allocation

1. Check for allocation failure
2. Clear the buffer contents, as they may actually be written to flash
3. Don't leak the buffer

Compile-tested only.

[ Tested successfully on my buggy ASUS machine - Matt ]

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 5ae2eb09419e..d2fbcedcf6ea 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -1069,7 +1069,10 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
                  * that by attempting to use more space than is available.
                  */
                 unsigned long dummy_size = remaining_size + 1024;
-                void *dummy = kmalloc(dummy_size, GFP_ATOMIC);
+                void *dummy = kzalloc(dummy_size, GFP_ATOMIC);
+
+                if (!dummy)
+                        return EFI_OUT_OF_RESOURCES;
 
                 status = efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
                                           EFI_VARIABLE_NON_VOLATILE |
@@ -1089,6 +1092,8 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
                                          0, dummy);
                 }
 
+                kfree(dummy);
+
                 /*
                  * The runtime code may now have triggered a garbage collection
                  * run, so check the variable info again