On Tue, Nov 11, 2008 at 04:40:43PM +0100, Kay Sievers wrote: > > I've made an image of a newly-formatted partition and posted it at > > http://launchpadlibrarian.net/19129151/sdb1.img.bz2 and the Ubuntu bug Thanks. > > (Thought you can > > force-mount it with a -t vfat.) > > > > ----- Forwarded message from Matthew Garrett <mjg59@xxxxxxxxxxxxx> ----- > > > > From: Matthew Garrett <mjg59@xxxxxxxxxxxxx> > > To: Matt Behrens <matt@xxxxxxxx> > > Subject: Re: LifeDrive and T|X not seen by hal > > > > Ok. The following things appear to be causing the failure: > > > > 1) The FAT signature in bytes 510 and 511 isn't present. This causes the > > code to bail. Right. # hexdump -s 0x1fe -n 5 -C /dev/loop0 000001fe 00 00 00 00 00 |.....| I'm not sure is the msdos signature (0x55 0xaa) at 510 and 511 is really mandatory. For example libblkid does not require this signature: # blkid /dev/loop0 /dev/loop0: LABEL="LIFEDRIVE" UUID="1234-5678" TYPE="vfat" when the standard FAT magic string is present. It works for years. > > 2) The FAT32 signature in the fsinfo block isn't present. This causes > > the code to bail. Right. Frankly, I have no clue why volume_id is checking also the FSInfo block. IMHO the FSInfo block is optional (if fsinfo_sector is zero) and should be _ignored_ when the signature does not match. See http://mail.opensolaris.org/pipermail/ufs-discuss/2007-February/000813.html The linux kernel also does not require valid FSInfo signature, the wrong signature is only reported: FAT: Invalid FSINFO signature: 0x00000000, 0x00000000 (sector = 1) and the FSInfo block is ignored at all. Fortunately, we check many other things (sector counts, number of FAT tabs, media check, cluster size, ...) in FAT super block. > Hmm, we can not really remove these checks, as there are many volumes > out there which we would detect as FAT, which are not FAT. Most of > these additional checks only got added after a several reports of > mis-detection. Even partition tables may get detected as FAT, if we > remove these checks, without adding new ones. The Palm uses the FAT32 magic string, so mis-detection based on bytes 510 and 511 shouldn't happen. > Maybe we should always probe for all known filesystems, and not stop > at the first match. And if we only find FAT, and nothing else, we Maybe for some cases. The mount(8) supports list of FS types. I can imagine that the library returns more results. It could be useful for example for CD-ROMs where is more filesystems. > might be able to say it's FAT even with less strict checks. Adding > Karel to Cc, because we plan to merge volume_id and blkid some day. Right now I'm working on regression tests ... so strange FS images are welcomed ;-) The patch below is for optimistic people :-) ./vol_id /dev/loop0 ID_FS_USAGE=filesystem ID_FS_TYPE=vfat ID_FS_VERSION=FAT32 ID_FS_UUID=1234-5678 ID_FS_UUID_ENC=1234-5678 ID_FS_LABEL=LIFEDRIVE ID_FS_LABEL_ENC=LIFEDRIVE ID_FS_LABEL_SAFE=LIFEDRIVE Karel >From 6147da52751e437e7f6aaa6f6f32253b35eed174 Mon Sep 17 00:00:00 2001 From: Karel Zak <kzak@xxxxxxxxxx> Date: Thu, 13 Nov 2008 13:07:48 +0100 Subject: [PATCH] volume_id: less paranoid FAT32 detection This patch * makes the msdos signature (0x55 0xaa) at 510 and 511 optional when the standard FAT magic string is present. * removes FSInfo block detection. The block is optional and should be ignored when the block signature is not valid. The block is not required by Linux kernel. Signed-off-by: Karel Zak <kzak@xxxxxxxxxx> --- extras/volume_id/lib/fat.c | 23 ++++------------------- 1 files changed, 4 insertions(+), 19 deletions(-) diff --git a/extras/volume_id/lib/fat.c b/extras/volume_id/lib/fat.c index 759e106..0685234 100644 --- a/extras/volume_id/lib/fat.c +++ b/extras/volume_id/lib/fat.c @@ -277,10 +277,6 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size) if (buf == NULL) return -1; - /* check signature */ - if (buf[510] != 0x55 || buf[511] != 0xaa) - return -1; - vs = (struct vfat_super_block *) buf; if (memcmp(vs->sysid, "NTFS", 4) == 0) return -1; @@ -301,6 +297,10 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size) if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0) goto magic; + /* check signature */ + if (buf[510] != 0x55 || buf[511] != 0xaa) + return -1; + /* some old floppies don't have a magic, expect the boot jump address to match */ if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) && vs->boot_jump[0] != 0xe9) @@ -404,21 +404,6 @@ magic: goto found; fat32: - /* FAT32 should have a valid signature in the fsinfo block */ - fsinfo_sect = le16_to_cpu(vs->type.fat32.fsinfo_sector); - buf = volume_id_get_buffer(id, off + (fsinfo_sect * sector_size), 0x200); - if (buf == NULL) - return -1; - fsinfo = (struct fat32_fsinfo *) buf; - if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0) - return -1; - if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0) - return -1 ; - - vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200); - if (vs == NULL) - return -1; - strcpy(id->type_version, "FAT32"); /* FAT32 root dir is a cluster chain like any other directory */ -- 1.5.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
