From 77648c5c01c79a330075824ff695ecd185514edc Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Jo=C3=A3o=20Paulo=20Rechi=20Vita?= <jprvita@endlessos.org>

Date: Fri, 15 Feb 2019 15:55:53 -0800

Subject: [PATCH 34/35] fallback: Use a dynamic buffer when list var names

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Now that we are iterating over all EFI variables to look for duplicate

boot entries, we should use a dynamic buffer, so if the firmware tells

us the buffer is too small for the next variable name we can re-allocate

it to a big enough size.

Signed-off-by: João Paulo Rechi Vita <jprvita@endlessos.org>

---

 fallback.c | 22 +++++++++++++++++-----

 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/fallback.c b/fallback.c

index feb15df5..801955c7 100644

--- a/fallback.c

+++ b/fallback.c

@@ -415,9 +415,12 @@ find_boot_option(EFI_DEVICE_PATH *dp, EFI_DEVICE_PATH *fulldp,

 	cursor += DevicePathSize(dp);

 	StrCpy((CHAR16 *)cursor, arguments);

-	CHAR16 varname[256];

 	EFI_STATUS efi_status;

 	EFI_GUID vendor_guid = NullGuid;

+	UINTN buffer_size = 256 * sizeof(CHAR16);

+	CHAR16 *varname = AllocateZeroPool(buffer_size);

+	if (!varname)

+		return EFI_OUT_OF_RESOURCES;

 	UINTN max_candidate_size = calc_masked_boot_option_size(size);

 	CHAR8 *candidate = AllocateZeroPool(max_candidate_size);

@@ -426,14 +429,22 @@ find_boot_option(EFI_DEVICE_PATH *dp, EFI_DEVICE_PATH *fulldp,

 		return EFI_OUT_OF_RESOURCES;

 	}

-	varname[0] = 0;

 	while (1) {

-		UINTN varname_size = sizeof(varname);

+		UINTN varname_size = buffer_size;

 		efi_status = gRT->GetNextVariableName(&varname_size, varname,

 						      &vendor_guid);

 		if (EFI_ERROR(efi_status)) {

-			if (efi_status == EFI_BUFFER_TOO_SMALL)

-				VerbosePrint(L"Buffer too small for next variable name\n");

+			if (efi_status == EFI_BUFFER_TOO_SMALL) {

+				VerbosePrint(L"Buffer too small for next variable name, re-allocating it to be %d bytes and retrying\n",

+					     varname_size);

+				varname = ReallocatePool(varname,

+							 buffer_size,

+							 varname_size);

+				if (!varname)

+					return EFI_OUT_OF_RESOURCES;

+				buffer_size = varname_size;

+				continue;

+			}

 			if (efi_status == EFI_DEVICE_ERROR)

 				VerbosePrint(L"The next variable name could not be retrieved due to a hardware error\n");

@@ -487,6 +498,7 @@ find_boot_option(EFI_DEVICE_PATH *dp, EFI_DEVICE_PATH *fulldp,

 	}

 	FreePool(candidate);

 	FreePool(data);

+	FreePool(varname);

 	return efi_status;

 }

-- 

2.32.0