Some UDF creators (specifically Microsoft, but perhaps others) mishandle
the ECMA-167 corner case that requires descriptors within a Volume
Recognition Sequence to be placed at 4096-byte intervals on media where
the block size is 4K. Instead, the descriptors are placed at the 2048-
byte interval mandated for media with smaller blocks. This nonconformity
currently prevents Linux from recognizing the filesystem as UDF.
Modify the driver to tolerate a misformatted VRS on 4K media.
[JK: Simplified descriptor checking]
Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
Tested-by: Steven J. Magnani <steve@digidescorp.com>
Link: https://lore.kernel.org/r/20190711133852.16887-2-steve@digidescorp.com
Signed-off-by: Jan Kara <jack@suse.cz>
vsd = (struct volStructDesc *)(bh->b_data +
(sector & (sb->s_blocksize - 1)));
nsr = identify_vsd(vsd);
+ /* Found NSR or end? */
+ if (nsr) {
+ brelse(bh);
+ break;
+ }
+ /*
+ * Special handling for improperly formatted VRS (e.g., Win10)
+ * where components are separated by 2048 bytes even though
+ * sectors are 4K
+ */
+ if (sb->s_blocksize == 4096) {
+ nsr = identify_vsd(vsd + 1);
+ /* Ignore unknown IDs... */
+ if (nsr < 0)
+ nsr = 0;
+ }
brelse(bh);
}