ext4: don't try to modify s_flags if the the file system is read-only (23301410) · Commits · 戴 / test

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:

"Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org

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);

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