From 190a8843ded231638d0e7ae7d8ca6a712472d114 Mon Sep 17 00:00:00 2001 From: Conrad Meyer Date: Fri, 6 Jun 2014 14:36:37 -0700 Subject: fs/fat/: add support for DOS 1.x formatted volumes Add structure for parsed BPB information, struct fat_bios_param_block, and move all of the deserialization and validation logic from fat_fill_super() into fat_read_bpb(). Add a 'dos1xfloppy' mount option to infer DOS 2.x BIOS Parameter Block defaults from block device geometry for ancient floppies and floppy images, as a fall-back from the default BPB parsing logic. When fat_read_bpb() finds an invalid FAT filesystem and dos1xfloppy is set, fall back to fat_read_static_bpb(). fat_read_static_bpb() validates that the entire BPB is zero, and that the floppy has a DOS-style 8086 code bootstrapping header. Then it fills in default BPB values from media size and a table.[0] Media size is assumed to be static for archaic FAT volumes. See also: [1]. Fixes kernel.org bug #42617. [0]: https://en.wikipedia.org/wiki/File_Allocation_Table#Exceptions [1]: http://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html [hirofumi@mail.parknet.co.jp: fix missed error code] Signed-off-by: Conrad Meyer Acked-by: OGAWA Hirofumi Signed-off-by: OGAWA Hirofumi Tested-by: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fat/fat.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'fs/fat/fat.h') diff --git a/fs/fat/fat.h b/fs/fat/fat.h index 7c31f4bc74a9..e0c4ba39a377 100644 --- a/fs/fat/fat.h +++ b/fs/fat/fat.h @@ -52,7 +52,8 @@ struct fat_mount_options { usefree:1, /* Use free_clusters for FAT32 */ tz_set:1, /* Filesystem timestamps' offset set */ rodir:1, /* allow ATTR_RO for directory */ - discard:1; /* Issue discard requests on deletions */ + discard:1, /* Issue discard requests on deletions */ + dos1xfloppy:1; /* Assume default BPB for DOS 1.x floppies */ }; #define FAT_HASH_BITS 8 -- cgit v1.2.3-70-g09d2