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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" <tytso@mit.edu>
Cc: stable@vger.kernel.org
This commit is contained in:
Theodore Ts'o 2014-02-12 12:16:04 -05:00
parent 30d29b119e
commit 2330141097
1 changed files with 13 additions and 7 deletions
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20
fs/ext4/super.c
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@ -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 */