From 23301410972330c0ae9a8afc379ba2005e249cc6 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Wed, 12 Feb 2014 12:16:04 -0500 Subject: [PATCH] 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: "Theodore Ts'o" Cc: stable@vger.kernel.org --- fs/ext4/super.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 1f7784de05b6c6..710fed2377d415 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3695,16 +3695,22 @@ 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; - 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) { + 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); - sbi->s_hash_unsigned = 3; + 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 */