Commit 6fbacb85 authored Jul 11, 2019 by Steven J. Magnani Committed by Jan Kara Jul 31, 2019

udf: support 2048-byte spacing of VRS descriptors on 4K media



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>

parent ba54aef0

fs/udf/super.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -739,6 +739,22 @@ static int udf_check_vsd(struct super_block *sb)
		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);
		}

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