partitions: read whole sector with EFI GPT header

The size of EFI GPT header is not static, but whole sector is
allocated for the header. The HeaderSize field must be greater
than 92 (= sizeof(struct gpt_header) and must be less than or
equal to the logical block size.

It means we have to read whole sector with the header, because the
header crc32 checksum is calculated according to HeaderSize.

For more details see UEFI standard (version 2.3, May 2009):
  - 5.3.1 GUID Format overview, page 93
  - Table 13. GUID Partition Table Header, page 96

Signed-off-by: Karel Zak <kzak@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/partitions/efi.c b/fs/partitions/efi.c
index 80eeff5fdfe0..49cfd5f54238 100644
--- a/fs/partitions/efi.c
+++ b/fs/partitions/efi.c
@@ -262,15 +262,16 @@ static gpt_header *
 alloc_read_gpt_header(struct block_device *bdev, u64 lba)
 {
         gpt_header *gpt;
+        unsigned ssz = bdev_logical_block_size(bdev);
+
         if (!bdev)
                 return NULL;
 
-        gpt = kzalloc(sizeof (gpt_header), GFP_KERNEL);
+        gpt = kzalloc(ssz, GFP_KERNEL);
         if (!gpt)
                 return NULL;
 
-        if (read_lba(bdev, lba, (u8 *) gpt,
-                     sizeof (gpt_header)) < sizeof (gpt_header)) {
+        if (read_lba(bdev, lba, (u8 *) gpt, ssz) < ssz) {
                 kfree(gpt);
                 gpt=NULL;
                 return NULL;