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: Jan Kara <jack@suse.cz>
diff --git a/fs/udf/udf_sb.h b/fs/udf/udf_sb.h
index 9424d7c..d12e507 100644
--- a/fs/udf/udf_sb.h
+++ b/fs/udf/udf_sb.h
@@ -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