Commit a9ad01bc authored by Jan Kara's avatar Jan Kara
Browse files

udf: Prevent write-unsupported filesystem to be remounted read-write 



There are certain filesystem features which we support for reading but
not for writing. We properly refuse to mount such filesystems read-write
however for some features (such as read-only partitions), we don't check
for these features when remounting the filesystem from read-only to
read-write. Thus such filesystems could be remounted read-write leading
to strange behavior (most likely crashes).

Fix the problem by marking in superblock whether the filesystem has some
features that are supported in read-only mode and check this flag during
remount.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 59fed3bf

fs/udf/super.c

+16 −14
Original line number Diff line number Diff line
@@ -613,14 +613,11 @@ static int udf_remount_fs(struct super_block *sb, int *flags, char *options) 
	struct udf_options uopt;

	struct udf_sb_info *sbi = UDF_SB(sb);

	int error = 0;

	struct logicalVolIntegrityDescImpUse *lvidiu = udf_sb_lvidiu(sb);



	sync_filesystem(sb);

	if (lvidiu) {

		int write_rev = le16_to_cpu(lvidiu->minUDFWriteRev);

		if (write_rev > UDF_MAX_WRITE_VERSION && !(*flags & SB_RDONLY))

	if (!(*flags & SB_RDONLY) && UDF_QUERY_FLAG(sb, UDF_FLAG_RW_INCOMPAT))

		return -EACCES;

	}



	sync_filesystem(sb);



	uopt.flags = sbi->s_flags;

	uopt.uid   = sbi->s_uid;
@@ -1257,6 +1254,7 @@ static int udf_load_partdesc(struct super_block *sb, sector_t block) 
			ret = -EACCES;

			goto out_bh;

		}

		UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);

		ret = udf_load_vat(sb, i, type1_idx);

		if (ret < 0)

			goto out_bh;
@@ -2155,11 +2153,13 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent) 
				UDF_MAX_READ_VERSION);

			ret = -EINVAL;

			goto error_out;

		} else if (minUDFWriteRev > UDF_MAX_WRITE_VERSION &&

			   !sb_rdonly(sb)) {

		} else if (minUDFWriteRev > UDF_MAX_WRITE_VERSION) {

			if (!sb_rdonly(sb)) {

				ret = -EACCES;

				goto error_out;

			}

			UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);

		}



		sbi->s_udfrev = minUDFWriteRev;
@@ -2176,11 +2176,13 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent) 
	}



	if (sbi->s_partmaps[sbi->s_partition].s_partition_flags &

			UDF_PART_FLAG_READ_ONLY &&

	    !sb_rdonly(sb)) {

			UDF_PART_FLAG_READ_ONLY) {

		if (!sb_rdonly(sb)) {

			ret = -EACCES;

			goto error_out;

		}

		UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);

	}



	if (udf_find_fileset(sb, &fileset, &rootdir)) {

		udf_warn(sb, "No fileset found\n");

fs/udf/udf_sb.h

+2 −0
Original line number Diff line number Diff line
@@ -30,6 +30,8 @@ 
#define UDF_FLAG_LASTBLOCK_SET	16

#define UDF_FLAG_BLOCKSIZE_SET	17

#define UDF_FLAG_INCONSISTENT	18

#define UDF_FLAG_RW_INCOMPAT	19	/* Set when we find RW incompatible

					 * feature */



#define UDF_PART_FLAG_UNALLOC_BITMAP	0x0001

#define UDF_PART_FLAG_UNALLOC_TABLE	0x0002

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