[PATCH v3] partitions/efi: Fix partition name parsing in GUID partition entry

[Nikolai Merinov <n.merinov@inango-systems.com>]

GUID partition entry defined to have a partition name as 36 UTF-16LE
code units. This means that on big-endian platforms ASCII symbols
would be read with 0xXX00 efi_char16_t character code. In order to
correctly extract ASCII characters from a partition name field we
should be converted from 16LE to CPU architecture.

The problem exists on all big endian platforms.

Signed-off-by: Nikolai Merinov <n.merinov@inango-systems.com>
---
 block/partitions/efi.c | 3 ++-
 block/partitions/efi.h | 2 +-
 include/linux/efi.h    | 5 +++++
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index db2fef7dfc47..f1d0820de844 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -715,7 +715,8 @@ int efi_partition(struct parsed_partitions *state)
 				ARRAY_SIZE(ptes[i].partition_name));
 		info->volname[label_max] = 0;
 		while (label_count < label_max) {
-			u8 c = ptes[i].partition_name[label_count] & 0xff;
+			u8 c = 0xff & efi_char16le_to_cpu(
+					ptes[i].partition_name[label_count]);
 			if (c && !isprint(c))
 				c = '!';
 			info->volname[label_count] = c;
diff --git a/block/partitions/efi.h b/block/partitions/efi.h
index 3e8576157575..4d4cae0bb79e 100644
--- a/block/partitions/efi.h
+++ b/block/partitions/efi.h
@@ -88,7 +88,7 @@ typedef struct _gpt_entry {
 	__le64 starting_lba;
 	__le64 ending_lba;
 	gpt_entry_attributes attributes;
-	efi_char16_t partition_name[72 / sizeof (efi_char16_t)];
+	efi_char16le_t partition_name[72 / sizeof(efi_char16le_t)];
 } __packed gpt_entry;
 
 typedef struct _gpt_mbr_record {
diff --git a/include/linux/efi.h b/include/linux/efi.h
index aa54586db7a5..47882f2d45db 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -45,9 +45,14 @@
 typedef unsigned long efi_status_t;
 typedef u8 efi_bool_t;
 typedef u16 efi_char16_t;		/* UNICODE character */
+typedef __le16 efi_char16le_t;		/* UTF16-LE */
+typedef __be16 efi_char16be_t;		/* UTF16-BE */
 typedef u64 efi_physical_addr_t;
 typedef void *efi_handle_t;
 
+#define efi_char16le_to_cpu le16_to_cpu
+#define efi_char16be_to_cpu be16_to_cpu
+
 /*
  * The UEFI spec and EDK2 reference implementation both define EFI_GUID as
  * struct { u32 a; u16; b; u16 c; u8 d[8]; }; and so the implied alignment
-- 
2.17.1