partitions/efi: Fix partition name parsing in GUID partition entry

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.

[ mingo: Minor edits. ]

Fixes: eec7ecfede74 ("genhd, efi: add efi partition metadata to hd_structs")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nikolai Merinov <n.merinov@inango-systems.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200308080859.21568-29-ardb@kernel.org
Link: https://lore.kernel.org/r/797777312.1324734.1582544319435.JavaMail.zimbra@inango-systems.com/

diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index db2fef7..b64bfdd 100644 (file)
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -657,6 +657,31 @@ static int find_valid_gpt(struct parsed_partitions *state, gpt_header **gpt,
 }
 
 /**
+ * utf16_le_to_7bit(): Naively converts a UTF-16LE string to 7-bit ASCII 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 7-bit
+ * ASCII characters and stores 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 +717,6 @@ 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 +737,7 @@ 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 3e85761..5fc62fd 100644 (file)
--- 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 {