[PATCH] cmd: efidebug: always check return code from get_variable()

[AKASHI Takahiro]

CID 316364 says:
> Null pointer dereferences  (FORWARD_NULL)
>	printf("Result total size: 0x%x\n", result->variable_total_size);
at do_efi_capsule_res().

The code is basically safe because a buffer for "result" is allocated
by malloc() and filled up by the second get_variable(), which fails any way
if the allocation has failed.

But the first (and second) get_variable() possibly returns an error other
than EFI_SUCCESS. We always need to check the return code from
get_variable() before accessing the data in "result".

While this change won't suppress CID 316364, the resulting code is much
safer.

Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
---
 cmd/efidebug.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/cmd/efidebug.c b/cmd/efidebug.c
index 9a2d4ddd5ef4..83bc2196a5a9 100644
--- a/cmd/efidebug.c
+++ b/cmd/efidebug.c
@@ -189,14 +189,16 @@ static int do_efi_capsule_res(struct cmd_tbl *cmdtp, int flag,
 	ret = EFI_CALL(RT->get_variable(var_name16, &guid, NULL, &size, NULL));
 	if (ret == EFI_BUFFER_TOO_SMALL) {
 		result = malloc(size);
+		if (!result)
+			return CMD_RET_FAILURE;
 		ret = EFI_CALL(RT->get_variable(var_name16, &guid, NULL, &size,
 						result));
-		if (ret != EFI_SUCCESS) {
-			free(result);
-			printf("Failed to get %ls\n", var_name16);
+	}
+	if (ret != EFI_SUCCESS) {
+		free(result);
+		printf("Failed to get %ls\n", var_name16);
 
-			return CMD_RET_FAILURE;
-		}
+		return CMD_RET_FAILURE;
 	}
 
 	printf("Result total size: 0x%x\n", result->variable_total_size);
-- 
2.28.0