linux-kernel - Re: [PATCH v6 3/3] fs: fat: add ioctl method in fat filesystem driver

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Date:   Tue, 09 Jan 2018 17:10:57 +0900
From:   OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:     ChenGuanqiao <chen.chenchacha@...mail.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 3/3] fs: fat: add ioctl method in fat filesystem driver

ChenGuanqiao <chen.chenchacha@...mail.com> writes:

> +static int fat_check_d_characters(char *label, unsigned long len)
> +{
> +	int i;
> +
> +	for (i=0; i<len; ++i) {

coding style. "i=0" to "i = 0", etc.

> +		switch (label[i]) {
> +		case '0' ... '9':
> +		case 'A' ... 'Z':
> +		case '_':
> +			continue;
> +		case 0x20:
> +			return 0;

Hm, stop check at ' '? What if "aaa b.%%%"?

> +static int fat_ioctl_get_volume_label(struct inode *inode,
> +				      u8 __user *vol_label)
> +{
> +	int err = 0;
> +	struct buffer_head *bh;
> +	struct msdos_dir_entry *de;

Hm, user has to care to open rootdir for this ioctl? Isn't it better to
force use the root inode?

> +	inode_lock_shared(inode);
> +	err = fat_scan_volume_label(inode, &bh, &de);
> +	if (err)
> +		goto out;
> +
> +	if (copy_to_user(vol_label, de->name, MSDOS_NAME))
> +		err = -EFAULT;

Better to copy to user buffer outside locking.

> +static int fat_ioctl_set_volume_label(struct file *file,
> +				      u8 __user *vol_label)
> +{
> +	int err = 0;
> +	u8 label[MSDOS_NAME];
> +	struct buffer_head *boot_bh;
> +	struct buffer_head *vol_bh;
> +	struct msdos_dir_entry *de;
> +	struct fat_boot_sector *b;
> +	struct inode *inode = file_inode(file);
> +	struct super_block *sb = inode->i_sb;
> +	struct msdos_sb_info *sbi = MSDOS_SB(sb);
> +
> +	if (inode->i_ino != MSDOS_ROOT_INO) {

Same with above, better to force use the root inode.

> +	down_write(&sb->s_umount);
> +	inode_lock(inode);
> +
> +	/* Updates root directory's vol_label */
> +	err = fat_scan_volume_label(inode, &vol_bh, &de);
> +	if (err) {
> +		/* Create volume label entry */
> +		struct timespec ts;
> +
> +		mutex_lock(&sbi->s_lock);

No need sbi->s_lock?

> +		ts = current_time(inode);
> +		err = fat_add_volume_label_entry(inode, label, &ts);
> +		mutex_unlock(&sbi->s_lock);
> +
> +		if (err)
> +			goto out_vol_brelse;
> +	} else {
> +		/* Write to root directory */
> +		lock_buffer(vol_bh);

No need lock_buffer()?

> +		memcpy(de->name, label, sizeof(de->name));

Probably, update timestamp?

> +		mark_buffer_dirty(vol_bh);
> +		unlock_buffer(vol_bh);
> +	}
> +
> +	/* Update sector's vol_label */
> +	boot_bh = sb_bread(sb, 0);
> +	if (boot_bh == NULL) {
> +		fat_msg(sb, KERN_ERR,
> +			"unable to read boot sector to write volume label");
> +		err = -EIO;
> +		goto out_boot_brelse;
> +	}
> +
> +	b = (struct fat_boot_sector *)boot_bh->b_data;
> +	lock_buffer(boot_bh);

No need lock_buffer()?

> +	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(boot_bh);
> +	unlock_buffer(boot_bh);
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>