[PATCH v3 0/2] fs: fat: add ioctl to modify fat filesystem partion volume label

[PATCH v3 0/2] fs: fat: add ioctl to modify fat filesystem partion volume label

[Chen Guanqiao]

The FAT filesystem partition volume label can be read with
FAT_IOCTL_GET_VOLUME_LABEL and written with FAT_IOCTL_SET_VOLUME_LABEL.

v3:
1. write volume label both boot sector and root directory.

v2:
1. add filesystem version check.
2. add diretory permissions check.
3. add volume label string check.
4. fixed part of return value.
5. fixed some indent issue.
6. remove sync_dirty_buffer().

Chen Guanqiao (2):
  fs: fat: add fat filesystem partition volume label in local structure
  fs: fat: add ioctl method in fat filesystem driver

 fs/fat/fat.h                  |   1 +
 fs/fat/file.c                 | 116 ++++++++++++++++++++++++++++++++++++++++++
 fs/fat/inode.c                |  15 ++++--
 include/uapi/linux/msdos_fs.h |   2 +
 4 files changed, 131 insertions(+), 3 deletions(-)

--
2.15.1

[PATCH v3 1/2] fs: fat: add fat filesystem partition volume label in local structure

[Chen Guanqiao]

Signed-off-by: Chen Guanqiao <chen.chenchacha@foxmail.com>
---
 fs/fat/fat.h                  |  1 +
 fs/fat/inode.c                | 15 ++++++++++++---
 include/uapi/linux/msdos_fs.h |  2 ++
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 8fc1093da47d..204012c94421 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -86,6 +86,7 @@ struct msdos_sb_info {
	int dir_per_block;	      /* dir entries per block */
	int dir_per_block_bits;	      /* log2(dir_per_block) */
	unsigned int vol_id;		/*volume ID*/
+	char vol_label[11];		/*volume label*/

	int fatent_shift;
	const struct fatent_operations *fatent_ops;
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 20a0a89eaca5..a97b6314ef33 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -45,12 +45,14 @@ struct fat_bios_param_block {

	u8	fat16_state;
	u32	fat16_vol_id;
+	u8	fat16_vol_label[11];

	u32	fat32_length;
	u32	fat32_root_cluster;
	u16	fat32_info_sector;
	u8	fat32_state;
	u32	fat32_vol_id;
+	u8	fat32_vol_label[11];
 };

 static int fat_default_codepage = CONFIG_FAT_DEFAULT_CODEPAGE;
@@ -1460,12 +1462,16 @@ static int fat_read_bpb(struct super_block *sb, struct fat_boot_sector *b,

	bpb->fat16_state = b->fat16.state;
	bpb->fat16_vol_id = get_unaligned_le32(b->fat16.vol_id);
+	memcpy(bpb->fat16_vol_label, b->fat16.vol_label,
+		   sizeof(bpb->fat16_vol_label));

	bpb->fat32_length = le32_to_cpu(b->fat32.length);
	bpb->fat32_root_cluster = le32_to_cpu(b->fat32.root_cluster);
	bpb->fat32_info_sector = le16_to_cpu(b->fat32.info_sector);
	bpb->fat32_state = b->fat32.state;
	bpb->fat32_vol_id = get_unaligned_le32(b->fat32.vol_id);
+	memcpy(bpb->fat32_vol_label, b->fat32.vol_label,
+		   sizeof(bpb->fat32_vol_label));

	/* Validate this looks like a FAT filesystem BPB */
	if (!bpb->fat_reserved) {
@@ -1723,11 +1729,14 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
		brelse(fsinfo_bh);
	}

-	/* interpret volume ID as a little endian 32 bit integer */
-	if (sbi->fat_bits == 32)
+	/* interpret volume ID and label as a little endian 32 bit integer */
+	if (sbi->fat_bits == 32) {
		sbi->vol_id = bpb.fat32_vol_id;
-	else /* fat 16 or 12 */
+		memcpy(sbi->vol_label, bpb.fat32_vol_label, sizeof(sbi->vol_label));
+	} else { /* fat 16 or 12 */
		sbi->vol_id = bpb.fat16_vol_id;
+		memcpy(sbi->vol_label, bpb.fat16_vol_label, sizeof(sbi->vol_label));
+	}

	sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry);
	sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;
diff --git a/include/uapi/linux/msdos_fs.h b/include/uapi/linux/msdos_fs.h
index a45d0754102e..90d2d6f3d908 100644
--- a/include/uapi/linux/msdos_fs.h
+++ b/include/uapi/linux/msdos_fs.h
@@ -107,6 +107,8 @@ struct __fat_dirent {
 #define FAT_IOCTL_SET_ATTRIBUTES	_IOW('r', 0x11, __u32)
 /*Android kernel has used 0x12, so we use 0x13*/
 #define FAT_IOCTL_GET_VOLUME_ID		_IOR('r', 0x13, __u32)
+#define FAT_IOCTL_GET_VOLUME_LABEL	_IOR('r', 0x14, __u8[11])
+#define FAT_IOCTL_SET_VOLUME_LABEL	_IOW('r', 0x15, __u8[11])

 struct fat_boot_sector {
	__u8	ignored[3];	/* Boot strap short or near jump */
--
2.15.1

[PATCH v3 2/2] fs: fat: add ioctl method in fat filesystem driver

[Chen Guanqiao]

Signed-off-by: Chen Guanqiao <chen.chenchacha@foxmail.com>
---
 fs/fat/file.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 4724cc9ad650..972f9aed5b46 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -20,6 +20,25 @@
 static long fat_fallocate(struct file *file, int mode,
			  loff_t offset, loff_t len);

+static int fat_check_volume_label(const char *label)
+{
+	int i;
+
+	for (i=0; i<11; ++i) {
+		switch (label[i]) {
+		case 0x20:
+		case 'A' ... 'Z':
+		case '0' ... '9':
+			continue;
+		case 0:
+			return 0;
+		default:
+			return -EINVAL;
+		}
+	}
+	return -EINVAL;
+}
+
 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
 {
	u32 attr;
@@ -121,10 +140,103 @@ static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
	return put_user(sbi->vol_id, user_attr);
 }

+static int fat_ioctl_get_volume_label(struct inode *inode,
+				      u8 __user *vol_label)
+{
+	int ret = 0;
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+
+	if (copy_to_user(vol_label, sbi->vol_label, sizeof(sbi->vol_label)))
+		ret = -EFAULT;
+
+	return ret;
+}
+
+static int fat_ioctl_set_volume_label(struct file *file,
+				      u8 __user *vol_label)
+{
+	int err;
+	u8 label[11];
+	struct buffer_head *bh;
+	struct fat_boot_sector *b;
+	struct msdos_dir_entry *entry;
+	struct inode *inode = file_inode(file);
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (copy_from_user(label, vol_label, sizeof(label))) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	if (fat_check_volume_label(label)) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+
+	inode_lock(inode);
+
+	if (sb_rdonly(inode->i_sb)) {
+		err = -EROFS;
+		goto out_unlock_inode;
+	}
+
+	/* handling sector's vol_label */
+	bh = sb_bread(inode->i_sb, 0);
+	if (bh == NULL) {
+		fat_msg(inode->i_sb, KERN_ERR,
+			"unable to read boot sector to write volume label");
+		err = -EFAULT;
+		goto out_unlock_inode;
+	}
+
+	b = (struct fat_boot_sector *) bh->b_data;
+
+	if (b->fat16.signature == 0x28 || b->fat32.signature == 0x28) {
+		fat_msg(inode->i_sb, KERN_ERR,
+			"volume label supported since OS/2 1.2 and MS-DOS 4.0 "
+			"and higher");
+		err = -EFAULT;
+		goto out_unlock_inode;
+	}
+
+	lock_buffer(bh);
+	if (sbi->fat_bits == 32)
+		memcpy(b->fat32.vol_label, label, sizeof(label));
+	else
+		memcpy(b->fat16.vol_label, label, sizeof(label));
+
+	mark_buffer_dirty(bh);
+	unlock_buffer(bh);
+	brelse(bh);
+
+	/* handling root directory's vol_label */
+	bh = sb_bread(sb, sbi->dir_start);
+	entry = &((struct msdos_dir_entry *)(bh->b_data))[0];
+
+	lock_buffer(bh);
+	memcpy(entry->name, label, sizeof(entry->name));
+	mark_buffer_dirty(bh);
+	unlock_buffer(bh);
+	brelse(bh);
+
+	memcpy(sbi->vol_label, label, sizeof(sbi->vol_label));
+
+ out_unlock_inode:
+	inode_unlock(inode);
+ out:
+	return err;
+}
+
 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
	struct inode *inode = file_inode(filp);
	u32 __user *user_attr = (u32 __user *)arg;
+	u8 __user *user_vol_label = (u8 __user *)arg;

	switch (cmd) {
	case FAT_IOCTL_GET_ATTRIBUTES:
@@ -133,6 +245,10 @@ long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
		return fat_ioctl_set_attributes(filp, user_attr);
	case FAT_IOCTL_GET_VOLUME_ID:
		return fat_ioctl_get_volume_id(inode, user_attr);
+	case FAT_IOCTL_GET_VOLUME_LABEL:
+		return fat_ioctl_get_volume_label(inode, user_vol_label);
+	case FAT_IOCTL_SET_VOLUME_LABEL:
+		return fat_ioctl_set_volume_label(filp, user_vol_label);
	default:
		return -ENOTTY;	/* Inappropriate ioctl for device */
	}
--
2.15.1

Re: [PATCH v3 2/2] fs: fat: add ioctl method in fat filesystem driver

[OGAWA Hirofumi]

Chen Guanqiao <chen.chenchacha@foxmail.com> writes:

> +static int fat_check_volume_label(const char *label)
> +{
> +	int i;
> +
> +	for (i=0; i<11; ++i) {
> +		switch (label[i]) {
> +		case 0x20:
> +		case 'A' ... 'Z':
> +		case '0' ... '9':
> +			continue;
> +		case 0:
> +			return 0;
> +		default:
> +			return -EINVAL;
> +		}
> +	}
> +	return -EINVAL;
> +}

This check is really work? Especially what Windows show if '\0' is
included in label?

> +static int fat_ioctl_get_volume_label(struct inode *inode,
> +				      u8 __user *vol_label)
> +{
> +	int ret = 0;
> +	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
> +
> +	if (copy_to_user(vol_label, sbi->vol_label, sizeof(sbi->vol_label)))
> +		ret = -EFAULT;
> +
> +	return ret;
> +}

This should handle the label in root dir too.

> +	inode_lock(inode);

Lock is not enough.

> +	if (sb_rdonly(inode->i_sb)) {
> +		err = -EROFS;
> +		goto out_unlock_inode;
> +	}

mnt_want_write_file() checks it already.

> +	/* handling sector's vol_label */
> +	bh = sb_bread(inode->i_sb, 0);
> +	if (bh == NULL) {
> +		fat_msg(inode->i_sb, KERN_ERR,
> +			"unable to read boot sector to write volume label");
> +		err = -EFAULT;

-EIO

> +	if (b->fat16.signature == 0x28 || b->fat32.signature == 0x28) {
> +		fat_msg(inode->i_sb, KERN_ERR,
> +			"volume label supported since OS/2 1.2 and MS-DOS 4.0 "
> +			"and higher");
> +		err = -EFAULT;
> +		goto out_unlock_inode;
> +	}

I don't know though, is this check necessary?

> +	/* handling root directory's vol_label */
> +	bh = sb_bread(sb, sbi->dir_start);
> +	entry = &((struct msdos_dir_entry *)(bh->b_data))[0];
> +
> +	lock_buffer(bh);
> +	memcpy(entry->name, label, sizeof(entry->name));
> +	mark_buffer_dirty(bh);
> +	unlock_buffer(bh);
> +	brelse(bh);

This totally doesn't work. Please check other implementations how to
handle label.

> + out_unlock_inode:
> +	inode_unlock(inode);

Missing release mnt_want_write_file().

Thanks.