libblkid: vfat: Fix reading FAT32 boot label

FAT32 can be formatted with boot sign 0x28 to indicate that only serial id
is present or with boot sign 0x29 which indicates that both boot label and
serial id is present.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>

diff --git a/libblkid/src/superblocks/vfat.c b/libblkid/src/superblocks/vfat.c
index 72e9b78c6cbb0ce1c0886cf87cbfda152dddfac9..71813485a031c1a799b2d1e1f085f76b9684c7b1 100644 (file)
--- a/libblkid/src/superblocks/vfat.c
+++ b/libblkid/src/superblocks/vfat.c
@@ -43,7 +43,9 @@ struct vfat_super_block {
 /* 30*/        uint16_t        vs_fsinfo_sector;
 /* 32*/        uint16_t        vs_backup_boot;
 /* 34*/        uint16_t        vs_reserved2[6];
-/* 40*/        unsigned char   vs_unknown[3];
+/* 40*/        unsigned char   vs_drive_number;
+/* 41*/        unsigned char   vs_boot_flags;
+/* 42*/        unsigned char   vs_ext_boot_sign; /* 0x28 - without vs_label/vs_magic; 0x29 - with */
 /* 43*/        unsigned char   vs_serno[4];
 /* 47*/        unsigned char   vs_label[11];
 /* 52*/        unsigned char   vs_magic[8];
@@ -387,7 +389,9 @@ static int probe_vfat(blkid_probe pr, const struct blkid_idmag *mag)
 
                version = "FAT32";
 
-               boot_label = vs->vs_label;
+               if (vs->vs_ext_boot_sign == 0x29)
+                       boot_label = vs->vs_label;
+
                vol_serno = vs->vs_serno;
 
                /*