Commit 33404a15 authored by Tetsuhiro Kohada's avatar Tetsuhiro Kohada Committed by Namjae Jeon
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exfat: separate the boot sector analysis 



Separate the boot sector analysis to read_boot_sector().
And add a check for the fs_name field.
Furthermore, add a strict consistency check, because overlapping areas
can cause serious corruption.

Signed-off-by: default avatarTetsuhiro Kohada <kohada.t2@gmail.com>
Reviewed-by: default avatarSungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: default avatarNamjae Jeon <namjae.jeon@samsung.com>
parent 181a9e80

fs/exfat/exfat_raw.h

+2 −0
Original line number Diff line number Diff line
@@ -10,11 +10,13 @@ 


#define BOOT_SIGNATURE		0xAA55

#define EXBOOT_SIGNATURE	0xAA550000

#define STR_EXFAT		"EXFAT   "	/* size should be 8 */



#define EXFAT_MAX_FILE_LEN	255



#define VOL_CLEAN		0x0000

#define VOL_DIRTY		0x0002

#define ERR_MEDIUM		0x0004



#define EXFAT_EOF_CLUSTER	0xFFFFFFFFu

#define EXFAT_BAD_CLUSTER	0xFFFFFFF7u

fs/exfat/super.c

+54 −43
Original line number Diff line number Diff line
@@ -366,25 +366,20 @@ static int exfat_read_root(struct inode *inode) 
	return 0;

}



static struct boot_sector *exfat_read_boot_with_logical_sector(

		struct super_block *sb)

static int exfat_calibrate_blocksize(struct super_block *sb, int logical_sect)

{

	struct exfat_sb_info *sbi = EXFAT_SB(sb);

	struct boot_sector *p_boot = (struct boot_sector *)sbi->boot_bh->b_data;

	unsigned short logical_sect = 0;



	logical_sect = 1 << p_boot->sect_size_bits;



	if (!is_power_of_2(logical_sect) ||

	    logical_sect < 512 || logical_sect > 4096) {

		exfat_err(sb, "bogus logical sector size %u", logical_sect);

		return NULL;

		return -EIO;

	}



	if (logical_sect < sb->s_blocksize) {

		exfat_err(sb, "logical sector size too small for device (logical sector size = %u)",

			  logical_sect);

		return NULL;

		return -EIO;

	}



	if (logical_sect > sb->s_blocksize) {
@@ -394,24 +389,20 @@ static struct boot_sector *exfat_read_boot_with_logical_sector( 
		if (!sb_set_blocksize(sb, logical_sect)) {

			exfat_err(sb, "unable to set blocksize %u",

				  logical_sect);

			return NULL;

			return -EIO;

		}

		sbi->boot_bh = sb_bread(sb, 0);

		if (!sbi->boot_bh) {

			exfat_err(sb, "unable to read boot sector (logical sector size = %lu)",

				  sb->s_blocksize);

			return NULL;

			return -EIO;

		}



		p_boot = (struct boot_sector *)sbi->boot_bh->b_data;

	}

	return p_boot;

	return 0;

}



/* mount the file system volume */

static int __exfat_fill_super(struct super_block *sb)

static int exfat_read_boot_sector(struct super_block *sb)

{

	int ret;

	struct boot_sector *p_boot;

	struct exfat_sb_info *sbi = EXFAT_SB(sb);
@@ -424,51 +415,41 @@ static int __exfat_fill_super(struct super_block *sb) 
		exfat_err(sb, "unable to read boot sector");

		return -EIO;

	}



	/* PRB is read */

	p_boot = (struct boot_sector *)sbi->boot_bh->b_data;



	/* check the validity of BOOT */

	if (le16_to_cpu((p_boot->signature)) != BOOT_SIGNATURE) {

		exfat_err(sb, "invalid boot record signature");

		ret = -EINVAL;

		goto free_bh;

		return -EINVAL;

	}





	/* check logical sector size */

	p_boot = exfat_read_boot_with_logical_sector(sb);

	if (!p_boot) {

		ret = -EIO;

		goto free_bh;

	if (memcmp(p_boot->fs_name, STR_EXFAT, BOOTSEC_FS_NAME_LEN)) {

		exfat_err(sb, "invalid fs_name"); /* fs_name may unprintable */

		return -EINVAL;

	}



	/*

	 * res_zero field must be filled with zero to prevent mounting

	 * must_be_zero field must be filled with zero to prevent mounting

	 * from FAT volume.

	 */

	if (memchr_inv(p_boot->must_be_zero, 0,

			sizeof(p_boot->must_be_zero))) {

		ret = -EINVAL;

		goto free_bh;

	}

	if (memchr_inv(p_boot->must_be_zero, 0, sizeof(p_boot->must_be_zero)))

		return -EINVAL;



	p_boot = (struct boot_sector *)p_boot;

	if (!p_boot->num_fats) {

	if (p_boot->num_fats != 1 && p_boot->num_fats != 2) {

		exfat_err(sb, "bogus number of FAT structure");

		ret = -EINVAL;

		goto free_bh;

		return -EINVAL;

	}



	sbi->sect_per_clus = 1 << p_boot->sect_per_clus_bits;

	sbi->sect_per_clus_bits = p_boot->sect_per_clus_bits;

	sbi->cluster_size_bits = sbi->sect_per_clus_bits + sb->s_blocksize_bits;

	sbi->cluster_size_bits = p_boot->sect_per_clus_bits +

		p_boot->sect_size_bits;

	sbi->cluster_size = 1 << sbi->cluster_size_bits;

	sbi->num_FAT_sectors = le32_to_cpu(p_boot->fat_length);

	sbi->FAT1_start_sector = le32_to_cpu(p_boot->fat_offset);

	sbi->FAT2_start_sector = p_boot->num_fats == 1 ?

		sbi->FAT1_start_sector :

			sbi->FAT1_start_sector + sbi->num_FAT_sectors;

	sbi->FAT2_start_sector = le32_to_cpu(p_boot->fat_offset);

	if (p_boot->num_fats == 2)

		sbi->FAT2_start_sector += sbi->num_FAT_sectors;

	sbi->data_start_sector = le32_to_cpu(p_boot->clu_offset);

	sbi->num_sectors = le64_to_cpu(p_boot->vol_length);

	/* because the cluster index starts with 2 */
@@ -483,15 +464,45 @@ static int __exfat_fill_super(struct super_block *sb) 
	sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;

	sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED;



	if (le16_to_cpu(p_boot->vol_flags) & VOL_DIRTY) {

		sbi->vol_flag |= VOL_DIRTY;

		exfat_warn(sb, "Volume was not properly unmounted. Some data may be corrupt. Please run fsck.");

	/* check consistencies */

	if (sbi->num_FAT_sectors << p_boot->sect_size_bits <

	    sbi->num_clusters * 4) {

		exfat_err(sb, "bogus fat length");

		return -EINVAL;

	}

	if (sbi->data_start_sector <

	    sbi->FAT1_start_sector + sbi->num_FAT_sectors * p_boot->num_fats) {

		exfat_err(sb, "bogus data start sector");

		return -EINVAL;

	}

	if (sbi->vol_flag & VOL_DIRTY)

		exfat_warn(sb, "Volume was not properly unmounted. Some data may be corrupt. Please run fsck.");

	if (sbi->vol_flag & ERR_MEDIUM)

		exfat_warn(sb, "Medium has reported failures. Some data may be lost.");



	/* exFAT file size is limited by a disk volume size */

	sb->s_maxbytes = (u64)(sbi->num_clusters - EXFAT_RESERVED_CLUSTERS) <<

		sbi->cluster_size_bits;



	/* check logical sector size */

	if (exfat_calibrate_blocksize(sb, 1 << p_boot->sect_size_bits))

		return -EIO;



	return 0;

}



/* mount the file system volume */

static int __exfat_fill_super(struct super_block *sb)

{

	int ret;

	struct exfat_sb_info *sbi = EXFAT_SB(sb);



	ret = exfat_read_boot_sector(sb);

	if (ret) {

		exfat_err(sb, "failed to read boot sector");

		goto free_bh;

	}



	ret = exfat_create_upcase_table(sb);

	if (ret) {

		exfat_err(sb, "failed to load upcase table");

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