[ 30/95] x86/efi: Fix dummy variable buffer allocation

[Greg Kroah-Hartman]

3.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>

commit b8cb62f82103083a6e8fa5470bfe634a2c06514d upstream.

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@xxxxxxxxxxxxxxx>
Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/platform/efi/efi.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -1059,7 +1059,10 @@ efi_status_t efi_query_variable_store(u3
 		 * 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 |
@@ -1079,6 +1082,8 @@ efi_status_t efi_query_variable_store(u3
 					 0, dummy);
 		}
 
+		kfree(dummy);
+
 		/*
 		 * The runtime code may now have triggered a garbage collection
 		 * run, so check the variable info again


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