[PATCH 2/4] efi/libstub: Parse builtin command line after bootloader provided one

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

When CONFIG_CMDLINE_EXTEND is set, the core kernel command line handling
logic appends CONFIG_CMDLINE to the bootloader provided command line.
The EFI stub does the opposite, and parses the builtin one first.

The usual behavior of command line options is that the last one takes
precedence if it appears multiple times, unless there is a meaningful
way to combine them. In either case, parsing the builtin command line
first while the core kernel does it in the opposite order is likely to
produce inconsistent results in such cases.

Therefore, switch the order in the stub to match the core kernel.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/firmware/efi/libstub/efi-stub.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index fc71dcab43e0..382b54f40603 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -126,28 +126,25 @@ efi_status_t efi_handle_cmdline(efi_loaded_image_t *image, char **cmdline_ptr)
 		return EFI_OUT_OF_RESOURCES;
 	}
 
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
+		status = efi_parse_options(cmdline);
+		if (status != EFI_SUCCESS)
+			goto fail_free_cmdline;
+	}
+
 	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
 	    IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
 	    cmdline[0] == 0) {
 		status = efi_parse_options(CONFIG_CMDLINE);
-		if (status != EFI_SUCCESS) {
-			efi_err("Failed to parse options\n");
-			goto fail_free_cmdline;
-		}
-	}
-
-	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
-		status = efi_parse_options(cmdline);
-		if (status != EFI_SUCCESS) {
-			efi_err("Failed to parse options\n");
+		if (status != EFI_SUCCESS)
 			goto fail_free_cmdline;
-		}
 	}
 
 	*cmdline_ptr = cmdline;
 	return EFI_SUCCESS;
 
 fail_free_cmdline:
+	efi_err("Failed to parse options\n");
 	efi_bs_call(free_pool, cmdline);
 	return status;
 }
-- 
2.47.0.338.g60cca15819-goog