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

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Date:   Sat, 23 Dec 2017 16:25:12 +0800
From:   Chen Guanqiao <chen.chenchacha@...mail.com>
To:     hirofumi@...l.parknet.co.jp
Cc:     linux-kernel@...r.kernel.org,
        Chen Guanqiao <chen.chenchacha@...mail.com>
Subject: [PATCH v3 2/2] fs: fat: add ioctl method in fat filesystem driver

Signed-off-by: Chen Guanqiao <chen.chenchacha@...mail.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