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Commit 23301410 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: don't try to modify s_flags if the the file system is read-only 



If an ext4 file system is created by some tool other than mke2fs
(perhaps by someone who has a pathalogical fear of the GPL) that
doesn't set one or the other of the EXT2_FLAGS_{UN}SIGNED_HASH flags,
and that file system is then mounted read-only, don't try to modify
the s_flags field.  Otherwise, if dm_verity is in use, the superblock
will change, causing an dm_verity failure.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
parent 30d29b11

fs/ext4/super.c

+13 −7
Original line number Diff line number Diff line
@@ -3695,17 +3695,23 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) 
	for (i = 0; i < 4; i++)

		sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);

	sbi->s_def_hash_version = es->s_def_hash_version;

	if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_DIR_INDEX)) {

		i = le32_to_cpu(es->s_flags);

		if (i & EXT2_FLAGS_UNSIGNED_HASH)

			sbi->s_hash_unsigned = 3;

		else if ((i & EXT2_FLAGS_SIGNED_HASH) == 0) {

#ifdef __CHAR_UNSIGNED__

		es->s_flags |= cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);

			if (!(sb->s_flags & MS_RDONLY))

				es->s_flags |=

					cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);

			sbi->s_hash_unsigned = 3;

#else

		es->s_flags |= cpu_to_le32(EXT2_FLAGS_SIGNED_HASH);

			if (!(sb->s_flags & MS_RDONLY))

				es->s_flags |=

					cpu_to_le32(EXT2_FLAGS_SIGNED_HASH);

#endif

		}

	}



	/* Handle clustersize */

	clustersize = BLOCK_SIZE << le32_to_cpu(es->s_log_cluster_size);