linux-kernel - Re: [PATCH v4 2/2] fs: fat: add ioctl method in fat filesystem driver

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Message-ID: <87po71wjk6.fsf@mail.parknet.co.jp>
Date:   Wed, 27 Dec 2017 01:16:57 +0900
From:   OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:     ChenGuanqiao <chen.chenchacha@...mail.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] fs: fat: add ioctl method in fat filesystem driver

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

> +static int fat_check_volume_label(const char *label)
> +{
> +	int i;
> +
> +	for (i=0; i<11; ++i) {
> +		if (islower(label[i]))
> +			return -EINVAL;
> +	}
> +	return 0;
> +}

What happen if '\0' is included, or invalid chars as FAT filename?

> +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;
> +	struct super_block *sb = inode->i_sb;
> +	struct msdos_sb_info *sbi = MSDOS_SB(sb);
> +
> +	if (sbi->fat_bits == 32)
> +		bh = sb_bread(sb, sbi->data_start);
> +	else
> +		bh = sb_bread(sb, sbi->dir_start);
> +
> +	if (bh == NULL) {
> +		fat_msg(sb, KERN_ERR, "unable to read root directory");
> +		err = -EIO;
> +		goto out;
> +	}
> +
> +	de = (struct msdos_dir_entry *)bh->b_data;

The volume label is not fixed place in root dir. You have to find
ATTR_VOLUME, but not ATTR_EXT.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>