ntfs3: enforce read-only when used as legacy ntfs driver

Ensure that ntfs3 is mounted read-only when it is used to provide the
legacy ntfs driver.

Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/ntfs3/ntfs_fs.h b/fs/ntfs3/ntfs_fs.h
index 79356fd29a14141de34ed006517b153fd9e4872b..184c8bc76b927d0f3376724efbaff79bfb33766b 100644 (file)
--- a/fs/ntfs3/ntfs_fs.h
+++ b/fs/ntfs3/ntfs_fs.h
@@ -1154,4 +1154,6 @@ static inline void le64_sub_cpu(__le64 *var, u64 val)
        *var = cpu_to_le64(le64_to_cpu(*var) - val);
 }
 
+bool is_legacy_ntfs(struct super_block *sb);
+
 #endif /* _LINUX_NTFS3_NTFS_FS_H */

diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 8d2e51bae2cbc7d0b9d3d32473c8e52a97d44e9a..b26d95a8d3274d061fc2f0dc2ba7f19cd385db8a 100644 (file)
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -408,6 +408,12 @@ static int ntfs_fs_reconfigure(struct fs_context *fc)
        struct ntfs_mount_options *new_opts = fc->fs_private;
        int ro_rw;
 
+       /* If ntfs3 is used as legacy ntfs enforce read-only mode. */
+       if (is_legacy_ntfs(sb)) {
+               fc->sb_flags |= SB_RDONLY;
+               goto out;
+       }
+
        ro_rw = sb_rdonly(sb) && !(fc->sb_flags & SB_RDONLY);
        if (ro_rw && (sbi->flags & NTFS_FLAGS_NEED_REPLAY)) {
                errorf(fc,
@@ -427,8 +433,6 @@ static int ntfs_fs_reconfigure(struct fs_context *fc)
                        fc,
                        "ntfs3: Cannot use different iocharset when remounting!");
 
-       sync_filesystem(sb);
-
        if (ro_rw && (sbi->volume.flags & VOLUME_FLAG_DIRTY) &&
            !new_opts->force) {
                errorf(fc,
@@ -436,6 +440,8 @@ static int ntfs_fs_reconfigure(struct fs_context *fc)
                return -EINVAL;
        }
 
+out:
+       sync_filesystem(sb);
        swap(sbi->options, fc->fs_private);
 
        return 0;
@@ -1613,6 +1619,8 @@ load_root:
        }
 #endif
 
+       if (is_legacy_ntfs(sb))
+               sb->s_flags |= SB_RDONLY;
        return 0;
 
 put_inode_out:
@@ -1730,7 +1738,7 @@ static const struct fs_context_operations ntfs_context_ops = {
  * This will called when mount/remount. We will first initialize
  * options so that if remount we can use just that.
  */
-static int ntfs_init_fs_context(struct fs_context *fc)
+static int __ntfs_init_fs_context(struct fs_context *fc)
 {
        struct ntfs_mount_options *opts;
        struct ntfs_sb_info *sbi;
@@ -1778,6 +1786,11 @@ free_opts:
        return -ENOMEM;
 }
 
+static int ntfs_init_fs_context(struct fs_context *fc)
+{
+       return __ntfs_init_fs_context(fc);
+}
+
 static void ntfs3_kill_sb(struct super_block *sb)
 {
        struct ntfs_sb_info *sbi = sb->s_fs_info;
@@ -1800,10 +1813,20 @@ static struct file_system_type ntfs_fs_type = {
 };
 
 #if IS_ENABLED(CONFIG_NTFS_FS)
+static int ntfs_legacy_init_fs_context(struct fs_context *fc)
+{
+       int ret;
+
+       ret = __ntfs_init_fs_context(fc);
+       /* If ntfs3 is used as legacy ntfs enforce read-only mode. */
+       fc->sb_flags |= SB_RDONLY;
+       return ret;
+}
+
 static struct file_system_type ntfs_legacy_fs_type = {
        .owner                  = THIS_MODULE,
        .name                   = "ntfs",
-       .init_fs_context        = ntfs_init_fs_context,
+       .init_fs_context        = ntfs_legacy_init_fs_context,
        .parameters             = ntfs_fs_parameters,
        .kill_sb                = ntfs3_kill_sb,
        .fs_flags               = FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
@@ -1821,9 +1844,14 @@ static inline void unregister_as_ntfs_legacy(void)
 {
        unregister_filesystem(&ntfs_legacy_fs_type);
 }
+bool is_legacy_ntfs(struct super_block *sb)
+{
+       return sb->s_type == &ntfs_legacy_fs_type;
+}
 #else
 static inline void register_as_ntfs_legacy(void) {}
 static inline void unregister_as_ntfs_legacy(void) {}
+bool is_legacy_ntfs(struct super_block *sb) { return false; }
 #endif