[PATCH 28/28] partitions/efi: Fix partition name parsing in GUID partition entry

Ard Biesheuvel
2020-03-08T08:10:50Z

From: 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.

Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Nikolai Merinov <n.merinov@inango-systems.com>
Fixes: eec7ecfede74 ("genhd, efi: add efi partition metadata to hd_structs")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/797777312.1324734.1582544319435.JavaMail.zimbra@inango-systems.com/
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
block/partitions/efi.c | 35 ++++++++++++++++++++++++++---------
block/partitions/efi.h | 2 +-
2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index db2fef7dfc47..d26a0654d7ca 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -656,6 +656,30 @@ static int find_valid_gpt(struct parsed_partitions *state, gpt_header **gpt,
return 0;
}

+/**
+ * utf16_le_to_7bit(): Naively converts UTF-16LE string to 7bit characters
+ * @in: input UTF-16LE string
+ * @size: size of the input string
+ * @out: output string ptr, should be capable to store @size+1 characters
+ *
+ * Description: Converts @size UTF16-LE symbols from @in string to 7bit
+ * characters and store them to @out. Adds trailing zero to @out array.
+ */
+static void utf16_le_to_7bit(const __le16 *in, unsigned int size, u8 *out)
+{
+ unsigned int i = 0;
+
+ out[size] = 0;
+ while (i < size) {
+ u8 c = le16_to_cpu(in[i]) & 0xff;
+
+ if (c && !isprint(c))
+ c = '!';
+ out[i] = c;
+ i++;
+ }
+}
+
/**
* efi_partition(struct parsed_partitions *state)
* @state: disk parsed partitions
@@ -692,7 +716,6 @@ int efi_partition(struct parsed_partitions *state)

for (i = 0; i < le32_to_cpu(gpt->num_partition_entries) && i < state->limit-1; i++) {
struct partition_meta_info *info;
- unsigned label_count = 0;
unsigned label_max;
u64 start = le64_to_cpu(ptes[i].starting_lba);
u64 size = le64_to_cpu(ptes[i].ending_lba) -
@@ -713,14 +736,8 @@ int efi_partition(struct parsed_partitions *state)
/* Naively convert UTF16-LE to 7 bits. */
label_max = min(ARRAY_SIZE(info->volname) - 1,
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;
- if (c && !isprint(c))
- c = '!';
- info->volname[label_count] = c;
- label_count++;
- }
+ utf16_le_to_7bit(ptes[i].partition_name, label_max,
+ info->volname);
state->parts[i + 1].has_info = true;
}
kfree(ptes);
diff --git a/block/partitions/efi.h b/block/partitions/efi.h
index 3e8576157575..0b6d5b7be111 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)];
+ __le16 partition_name[72 / sizeof (__le16)];
} __packed gpt_entry;

typedef struct _gpt_mbr_record {
--
2.17.1