[PATCH 1/4 v2] exfat: redefine PBR as boot_sector

[PATCH 1/4 v2] exfat: redefine PBR as boot_sector

[Tetsuhiro Kohada]

Aggregate PBR related definitions and redefine as "boot_sector" to comply
with the exFAT specification.
And, rename variable names including 'pbr'.

Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
---
Changes in v2:
 - rebase with patch 'optimize dir-cache' applied

 fs/exfat/exfat_fs.h  |  2 +-
 fs/exfat/exfat_raw.h | 79 +++++++++++++++--------------------------
 fs/exfat/super.c     | 84 ++++++++++++++++++++++----------------------
 3 files changed, 72 insertions(+), 93 deletions(-)

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 5caad1380818..9673e2d31045 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -227,7 +227,7 @@ struct exfat_sb_info {
 	unsigned int root_dir; /* root dir cluster */
 	unsigned int dentries_per_clu; /* num of dentries per cluster */
 	unsigned int vol_flag; /* volume dirty flag */
-	struct buffer_head *pbr_bh; /* buffer_head of PBR sector */
+	struct buffer_head *boot_bh; /* buffer_head of BOOT sector */
 
 	unsigned int map_clu; /* allocation bitmap start cluster */
 	unsigned int map_sectors; /* num of allocation bitmap sectors */
diff --git a/fs/exfat/exfat_raw.h b/fs/exfat/exfat_raw.h
index 8d6c64a7546d..b373dc4e099f 100644
--- a/fs/exfat/exfat_raw.h
+++ b/fs/exfat/exfat_raw.h
@@ -8,7 +8,8 @@
 
 #include <linux/types.h>
 
-#define PBR_SIGNATURE		0xAA55
+#define BOOT_SIGNATURE		0xAA55
+#define EXBOOT_SIGNATURE	0xAA550000
 
 #define EXFAT_MAX_FILE_LEN	255
 
@@ -55,7 +56,7 @@
 
 /* checksum types */
 #define CS_DIR_ENTRY		0
-#define CS_PBR_SECTOR		1
+#define CS_BOOT_SECTOR		1
 #define CS_DEFAULT		2
 
 /* file attributes */
@@ -69,57 +70,35 @@
 #define ATTR_RWMASK		(ATTR_HIDDEN | ATTR_SYSTEM | ATTR_VOLUME | \
 				 ATTR_SUBDIR | ATTR_ARCHIVE)
 
-#define PBR64_JUMP_BOOT_LEN		3
-#define PBR64_OEM_NAME_LEN		8
-#define PBR64_RESERVED_LEN		53
+#define BOOTSEC_JUMP_BOOT_LEN		3
+#define BOOTSEC_OEM_NAME_LEN		8
+#define BOOTSEC_OLDBPB_LEN		53
 
 #define EXFAT_FILE_NAME_LEN		15
 
-/* EXFAT BIOS parameter block (64 bytes) */
-struct bpb64 {
-	__u8 jmp_boot[PBR64_JUMP_BOOT_LEN];
-	__u8 oem_name[PBR64_OEM_NAME_LEN];
-	__u8 res_zero[PBR64_RESERVED_LEN];
-} __packed;
-
-/* EXFAT EXTEND BIOS parameter block (56 bytes) */
-struct bsx64 {
-	__le64 vol_offset;
-	__le64 vol_length;
-	__le32 fat_offset;
-	__le32 fat_length;
-	__le32 clu_offset;
-	__le32 clu_count;
-	__le32 root_cluster;
-	__le32 vol_serial;
-	__u8 fs_version[2];
-	__le16 vol_flags;
-	__u8 sect_size_bits;
-	__u8 sect_per_clus_bits;
-	__u8 num_fats;
-	__u8 phy_drv_no;
-	__u8 perc_in_use;
-	__u8 reserved2[7];
-} __packed;
-
-/* EXFAT PBR[BPB+BSX] (120 bytes) */
-struct pbr64 {
-	struct bpb64 bpb;
-	struct bsx64 bsx;
-} __packed;
-
-/* Common PBR[Partition Boot Record] (512 bytes) */
-struct pbr {
-	union {
-		__u8 raw[64];
-		struct bpb64 f64;
-	} bpb;
-	union {
-		__u8 raw[56];
-		struct bsx64 f64;
-	} bsx;
-	__u8 boot_code[390];
-	__le16 signature;
+/* EXFAT: Main and Backup Boot Sector (512 bytes) */
+struct boot_sector {
+	__u8	jmp_boot[BOOTSEC_JUMP_BOOT_LEN];
+	__u8	oem_name[BOOTSEC_OEM_NAME_LEN];
+	__u8	must_be_zero[BOOTSEC_OLDBPB_LEN];
+	__le64	partition_offset;
+	__le64	vol_length;
+	__le32	fat_offset;
+	__le32	fat_length;
+	__le32	clu_offset;
+	__le32	clu_count;
+	__le32	root_cluster;
+	__le32	vol_serial;
+	__u8	fs_revision[2];
+	__le16	vol_flags;
+	__u8	sect_size_bits;
+	__u8	sect_per_clus_bits;
+	__u8	num_fats;
+	__u8	drv_sel;
+	__u8	percent_in_use;
+	__u8	reserved[7];
+	__u8	boot_code[390];
+	__le16	signature;
 } __packed;
 
 struct exfat_dentry {
diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index c1f47f4071a8..e60d28e73ff0 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -49,7 +49,7 @@ static void exfat_put_super(struct super_block *sb)
 		sync_blockdev(sb->s_bdev);
 	exfat_set_vol_flags(sb, VOL_CLEAN);
 	exfat_free_bitmap(sbi);
-	brelse(sbi->pbr_bh);
+	brelse(sbi->boot_bh);
 	mutex_unlock(&sbi->s_lock);
 
 	call_rcu(&sbi->rcu, exfat_delayed_free);
@@ -101,7 +101,7 @@ static int exfat_statfs(struct dentry *dentry, struct kstatfs *buf)
 int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
-	struct pbr64 *bpb = (struct pbr64 *)sbi->pbr_bh->b_data;
+	struct boot_sector *p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
 	bool sync;
 
 	/* flags are not changed */
@@ -116,18 +116,18 @@ int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag)
 	if (sb_rdonly(sb))
 		return 0;
 
-	bpb->bsx.vol_flags = cpu_to_le16(new_flag);
+	p_boot->vol_flags = cpu_to_le16(new_flag);
 
-	if (new_flag == VOL_DIRTY && !buffer_dirty(sbi->pbr_bh))
+	if (new_flag == VOL_DIRTY && !buffer_dirty(sbi->boot_bh))
 		sync = true;
 	else
 		sync = false;
 
-	set_buffer_uptodate(sbi->pbr_bh);
-	mark_buffer_dirty(sbi->pbr_bh);
+	set_buffer_uptodate(sbi->boot_bh);
+	mark_buffer_dirty(sbi->boot_bh);
 
 	if (sync)
-		sync_dirty_buffer(sbi->pbr_bh);
+		sync_dirty_buffer(sbi->boot_bh);
 	return 0;
 }
 
@@ -366,13 +366,14 @@ static int exfat_read_root(struct inode *inode)
 	return 0;
 }
 
-static struct pbr *exfat_read_pbr_with_logical_sector(struct super_block *sb)
+static struct boot_sector *exfat_read_boot_with_logical_sector(
+		struct super_block *sb)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
-	struct pbr *p_pbr = (struct pbr *) (sbi->pbr_bh)->b_data;
+	struct boot_sector *p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
 	unsigned short logical_sect = 0;
 
-	logical_sect = 1 << p_pbr->bsx.f64.sect_size_bits;
+	logical_sect = 1 << p_boot->sect_size_bits;
 
 	if (!is_power_of_2(logical_sect) ||
 	    logical_sect < 512 || logical_sect > 4096) {
@@ -387,49 +388,48 @@ static struct pbr *exfat_read_pbr_with_logical_sector(struct super_block *sb)
 	}
 
 	if (logical_sect > sb->s_blocksize) {
-		brelse(sbi->pbr_bh);
-		sbi->pbr_bh = NULL;
+		brelse(sbi->boot_bh);
+		sbi->boot_bh = NULL;
 
 		if (!sb_set_blocksize(sb, logical_sect)) {
 			exfat_err(sb, "unable to set blocksize %u",
 				  logical_sect);
 			return NULL;
 		}
-		sbi->pbr_bh = sb_bread(sb, 0);
-		if (!sbi->pbr_bh) {
+		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;
 		}
 
-		p_pbr = (struct pbr *)sbi->pbr_bh->b_data;
+		p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
 	}
-	return p_pbr;
+	return p_boot;
 }
 
 /* mount the file system volume */
 static int __exfat_fill_super(struct super_block *sb)
 {
 	int ret;
-	struct pbr *p_pbr;
-	struct pbr64 *p_bpb;
+	struct boot_sector *p_boot;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 
 	/* set block size to read super block */
 	sb_min_blocksize(sb, 512);
 
 	/* read boot sector */
-	sbi->pbr_bh = sb_bread(sb, 0);
-	if (!sbi->pbr_bh) {
+	sbi->boot_bh = sb_bread(sb, 0);
+	if (!sbi->boot_bh) {
 		exfat_err(sb, "unable to read boot sector");
 		return -EIO;
 	}
 
 	/* PRB is read */
-	p_pbr = (struct pbr *)sbi->pbr_bh->b_data;
+	p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
 
-	/* check the validity of PBR */
-	if (le16_to_cpu((p_pbr->signature)) != PBR_SIGNATURE) {
+	/* 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;
@@ -437,8 +437,8 @@ static int __exfat_fill_super(struct super_block *sb)
 
 
 	/* check logical sector size */
-	p_pbr = exfat_read_pbr_with_logical_sector(sb);
-	if (!p_pbr) {
+	p_boot = exfat_read_boot_with_logical_sector(sb);
+	if (!p_boot) {
 		ret = -EIO;
 		goto free_bh;
 	}
@@ -447,43 +447,43 @@ static int __exfat_fill_super(struct super_block *sb)
 	 * res_zero field must be filled with zero to prevent mounting
 	 * from FAT volume.
 	 */
-	if (memchr_inv(p_pbr->bpb.f64.res_zero, 0,
-			sizeof(p_pbr->bpb.f64.res_zero))) {
+	if (memchr_inv(p_boot->must_be_zero, 0,
+			sizeof(p_boot->must_be_zero))) {
 		ret = -EINVAL;
 		goto free_bh;
 	}
 
-	p_bpb = (struct pbr64 *)p_pbr;
-	if (!p_bpb->bsx.num_fats) {
+	p_boot = (struct boot_sector *)p_boot;
+	if (!p_boot->num_fats) {
 		exfat_err(sb, "bogus number of FAT structure");
 		ret = -EINVAL;
 		goto free_bh;
 	}
 
-	sbi->sect_per_clus = 1 << p_bpb->bsx.sect_per_clus_bits;
-	sbi->sect_per_clus_bits = p_bpb->bsx.sect_per_clus_bits;
+	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 = 1 << sbi->cluster_size_bits;
-	sbi->num_FAT_sectors = le32_to_cpu(p_bpb->bsx.fat_length);
-	sbi->FAT1_start_sector = le32_to_cpu(p_bpb->bsx.fat_offset);
-	sbi->FAT2_start_sector = p_bpb->bsx.num_fats == 1 ?
+	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->data_start_sector = le32_to_cpu(p_bpb->bsx.clu_offset);
-	sbi->num_sectors = le64_to_cpu(p_bpb->bsx.vol_length);
+	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 */
-	sbi->num_clusters = le32_to_cpu(p_bpb->bsx.clu_count) +
+	sbi->num_clusters = le32_to_cpu(p_boot->clu_count) +
 		EXFAT_RESERVED_CLUSTERS;
 
-	sbi->root_dir = le32_to_cpu(p_bpb->bsx.root_cluster);
+	sbi->root_dir = le32_to_cpu(p_boot->root_cluster);
 	sbi->dentries_per_clu = 1 <<
 		(sbi->cluster_size_bits - DENTRY_SIZE_BITS);
 
-	sbi->vol_flag = le16_to_cpu(p_bpb->bsx.vol_flags);
+	sbi->vol_flag = le16_to_cpu(p_boot->vol_flags);
 	sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;
 	sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED;
 
-	if (le16_to_cpu(p_bpb->bsx.vol_flags) & VOL_DIRTY) {
+	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.");
 	}
@@ -517,7 +517,7 @@ static int __exfat_fill_super(struct super_block *sb)
 free_upcase_table:
 	exfat_free_upcase_table(sbi);
 free_bh:
-	brelse(sbi->pbr_bh);
+	brelse(sbi->boot_bh);
 	return ret;
 }
 
@@ -608,7 +608,7 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc)
 free_table:
 	exfat_free_upcase_table(sbi);
 	exfat_free_bitmap(sbi);
-	brelse(sbi->pbr_bh);
+	brelse(sbi->boot_bh);
 
 check_nls_io:
 	unload_nls(sbi->nls_io);
-- 
2.25.1

[PATCH 2/4 v2] exfat: separate the boot sector analysis

[Tetsuhiro Kohada]

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

Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
---
Changes in v2:
 - rebase with patch 'optimize dir-cache' applied

 fs/exfat/exfat_raw.h |  1 +
 fs/exfat/super.c     | 96 +++++++++++++++++++++++---------------------
 2 files changed, 52 insertions(+), 45 deletions(-)

diff --git a/fs/exfat/exfat_raw.h b/fs/exfat/exfat_raw.h
index b373dc4e099f..65f884785192 100644
--- a/fs/exfat/exfat_raw.h
+++ b/fs/exfat/exfat_raw.h
@@ -15,6 +15,7 @@
 
 #define VOL_CLEAN		0x0000
 #define VOL_DIRTY		0x0002
+#define ERR_MEDIUM		0x0004
 
 #define EXFAT_EOF_CLUSTER	0xFFFFFFFFu
 #define EXFAT_BAD_CLUSTER	0xFFFFFFF7u
diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index e60d28e73ff0..95909b4d5e75 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -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 +415,36 @@ 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;
-	}
-
-
-	/* check logical sector size */
-	p_boot = exfat_read_boot_with_logical_sector(sb);
-	if (!p_boot) {
-		ret = -EIO;
-		goto free_bh;
+		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 +459,45 @@ 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");
-- 
2.25.1

[PATCH 3/4 v2] exfat: add boot region verification

[Tetsuhiro Kohada]

Add Boot-Regions verification specified in exFAT specification.
Note that the checksum type is strongly related to the raw structure,
so the'u32 'type is used to clarify the number of bits.

Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
---
Changes in v2:
 - rebase with patch 'optimize dir-cache' applied
 - just print a warning when invalid exboot-signature detected
 - print additional information when invalid boot-checksum detected

 fs/exfat/exfat_fs.h |  1 +
 fs/exfat/misc.c     | 14 +++++++++++++
 fs/exfat/super.c    | 49 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 9673e2d31045..eebbe5a84b2b 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -514,6 +514,7 @@ void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
 		u8 *tz, __le16 *time, __le16 *date, u8 *time_cs);
 unsigned short exfat_calc_chksum_2byte(void *data, int len,
 		unsigned short chksum, int type);
+u32 exfat_calc_chksum32(void *data, int len, u32 chksum, int type);
 void exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync);
 void exfat_chain_set(struct exfat_chain *ec, unsigned int dir,
 		unsigned int size, unsigned char flags);
diff --git a/fs/exfat/misc.c b/fs/exfat/misc.c
index ab7f88b1f6d3..b82d2dd5bd7c 100644
--- a/fs/exfat/misc.c
+++ b/fs/exfat/misc.c
@@ -151,6 +151,20 @@ unsigned short exfat_calc_chksum_2byte(void *data, int len,
 	return chksum;
 }
 
+u32 exfat_calc_chksum32(void *data, int len, u32 chksum, int type)
+{
+	int i;
+	u8 *c = (u8 *)data;
+
+	for (i = 0; i < len; i++, c++) {
+		if (unlikely(type == CS_BOOT_SECTOR &&
+			     (i == 106 || i == 107 || i == 112)))
+			continue;
+		chksum = ((chksum << 31) | (chksum >> 1)) + *c;
+	}
+	return chksum;
+}
+
 void exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync)
 {
 	set_bit(EXFAT_SB_DIRTY, &EXFAT_SB(sb)->s_state);
diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index 95909b4d5e75..381f4394f976 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -486,6 +486,49 @@ static int exfat_read_boot_sector(struct super_block *sb)
 	return 0;
 }
 
+static int exfat_verify_boot_region(struct super_block *sb)
+{
+	struct buffer_head *bh = NULL;
+	u32 chksum = 0, *p_sig, *p_chksum;
+	int sn, i;
+
+	/* read boot sector sub-regions */
+	for (sn = 0; sn < 11; sn++) {
+		bh = sb_bread(sb, sn);
+		if (!bh)
+			return -EIO;
+
+		if (sn != 0 && sn <= 8) {
+			/* extended boot sector sub-regions */
+			p_sig = (u32 *)&bh->b_data[sb->s_blocksize - 4];
+			if (le32_to_cpu(*p_sig) != EXBOOT_SIGNATURE)
+				exfat_warn(sb, "Invalid exboot-signature(sector = %d): 0x%08x",
+					   sn, le32_to_cpu(*p_sig));
+		}
+
+		chksum = exfat_calc_chksum32(bh->b_data, sb->s_blocksize,
+			chksum, sn ? CS_DEFAULT : CS_BOOT_SECTOR);
+		brelse(bh);
+	}
+
+	/* boot checksum sub-regions */
+	bh = sb_bread(sb, sn);
+	if (!bh)
+		return -EIO;
+
+	for (i = 0; i < sb->s_blocksize; i += sizeof(u32)) {
+		p_chksum = (u32 *)&bh->b_data[i];
+		if (le32_to_cpu(*p_chksum) != chksum) {
+			exfat_err(sb, "Invalid boot checksum (boot checksum : 0x%08x, checksum : 0x%08x)",
+				  le32_to_cpu(*p_chksum), chksum);
+			brelse(bh);
+			return -EINVAL;
+		}
+	}
+	brelse(bh);
+	return 0;
+}
+
 /* mount the file system volume */
 static int __exfat_fill_super(struct super_block *sb)
 {
@@ -498,6 +541,12 @@ static int __exfat_fill_super(struct super_block *sb)
 		goto free_bh;
 	}
 
+	ret = exfat_verify_boot_region(sb);
+	if (ret) {
+		exfat_err(sb, "invalid boot region");
+		goto free_bh;
+	}
+
 	ret = exfat_create_upcase_table(sb);
 	if (ret) {
 		exfat_err(sb, "failed to load upcase table");
-- 
2.25.1

[PATCH 4/4 v2] exfat: standardize checksum calculation

[Tetsuhiro Kohada]

To clarify that it is a 16-bit checksum, the parts related to the 16-bit
checksum are renamed and change type to u16.
Furthermore, replace checksum calculation in exfat_load_upcase_table()
with exfat_calc_checksum32().

Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
---
Changes in v2:
 - rebase with patch 'optimize dir-cache' applied

 fs/exfat/dir.c      | 12 ++++++------
 fs/exfat/exfat_fs.h |  5 ++---
 fs/exfat/misc.c     | 10 ++++------
 fs/exfat/nls.c      | 19 +++++++------------
 4 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 2902d285bf20..de43534aa299 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -491,7 +491,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,
 	int ret = 0;
 	int i, num_entries;
 	sector_t sector;
-	unsigned short chksum;
+	u16 chksum;
 	struct exfat_dentry *ep, *fep;
 	struct buffer_head *fbh, *bh;
 
@@ -500,7 +500,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,
 		return -EIO;
 
 	num_entries = fep->dentry.file.num_ext + 1;
-	chksum = exfat_calc_chksum_2byte(fep, DENTRY_SIZE, 0, CS_DIR_ENTRY);
+	chksum = exfat_calc_chksum16(fep, DENTRY_SIZE, 0, CS_DIR_ENTRY);
 
 	for (i = 1; i < num_entries; i++) {
 		ep = exfat_get_dentry(sb, p_dir, entry + i, &bh, NULL);
@@ -508,7 +508,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,
 			ret = -EIO;
 			goto release_fbh;
 		}
-		chksum = exfat_calc_chksum_2byte(ep, DENTRY_SIZE, chksum,
+		chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,
 				CS_DEFAULT);
 		brelse(bh);
 	}
@@ -593,8 +593,8 @@ void exfat_update_dir_chksum_with_entry_set(struct exfat_entry_set_cache *es)
 
 	for (i = 0; i < es->num_entries; i++) {
 		ep = exfat_get_dentry_cached(es, i);
-		chksum = exfat_calc_chksum_2byte(ep, DENTRY_SIZE, chksum,
-						 chksum_type);
+		chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,
+					     chksum_type);
 		chksum_type = CS_DEFAULT;
 	}
 	ep = exfat_get_dentry_cached(es, 0);
@@ -1000,7 +1000,7 @@ int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei,
 			}
 
 			if (entry_type == TYPE_STREAM) {
-				unsigned short name_hash;
+				u16 name_hash;
 
 				if (step != DIRENT_STEP_STRM) {
 					step = DIRENT_STEP_FILE;
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index eebbe5a84b2b..9188985694f0 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -137,7 +137,7 @@ struct exfat_dentry_namebuf {
 struct exfat_uni_name {
 	/* +3 for null and for converting */
 	unsigned short name[MAX_NAME_LENGTH + 3];
-	unsigned short name_hash;
+	u16 name_hash;
 	unsigned char name_len;
 };
 
@@ -512,8 +512,7 @@ void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
 void exfat_truncate_atime(struct timespec64 *ts);
 void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
 		u8 *tz, __le16 *time, __le16 *date, u8 *time_cs);
-unsigned short exfat_calc_chksum_2byte(void *data, int len,
-		unsigned short chksum, int type);
+u16 exfat_calc_chksum16(void *data, int len, u16 chksum, int type);
 u32 exfat_calc_chksum32(void *data, int len, u32 chksum, int type);
 void exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync);
 void exfat_chain_set(struct exfat_chain *ec, unsigned int dir,
diff --git a/fs/exfat/misc.c b/fs/exfat/misc.c
index b82d2dd5bd7c..17d41f3d3709 100644
--- a/fs/exfat/misc.c
+++ b/fs/exfat/misc.c
@@ -136,17 +136,15 @@ void exfat_truncate_atime(struct timespec64 *ts)
 	ts->tv_nsec = 0;
 }
 
-unsigned short exfat_calc_chksum_2byte(void *data, int len,
-		unsigned short chksum, int type)
+u16 exfat_calc_chksum16(void *data, int len, u16 chksum, int type)
 {
 	int i;
-	unsigned char *c = (unsigned char *)data;
+	u8 *c = (u8 *)data;
 
 	for (i = 0; i < len; i++, c++) {
-		if (((i == 2) || (i == 3)) && (type == CS_DIR_ENTRY))
+		if (unlikely(type == CS_DIR_ENTRY && (i == 2 || i == 3)))
 			continue;
-		chksum = (((chksum & 1) << 15) | ((chksum & 0xFFFE) >> 1)) +
-			(unsigned short)*c;
+		chksum = ((chksum << 15) | (chksum >> 1)) + *c;
 	}
 	return chksum;
 }
diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c
index 1ebda90cbdd7..19321773dd07 100644
--- a/fs/exfat/nls.c
+++ b/fs/exfat/nls.c
@@ -527,7 +527,7 @@ static int exfat_utf8_to_utf16(struct super_block *sb,
 
 	*uniname = '\0';
 	p_uniname->name_len = unilen;
-	p_uniname->name_hash = exfat_calc_chksum_2byte(upname, unilen << 1, 0,
+	p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0,
 			CS_DEFAULT);
 
 	if (p_lossy)
@@ -623,7 +623,7 @@ static int exfat_nls_to_ucs2(struct super_block *sb,
 
 	*uniname = '\0';
 	p_uniname->name_len = unilen;
-	p_uniname->name_hash = exfat_calc_chksum_2byte(upname, unilen << 1, 0,
+	p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0,
 			CS_DEFAULT);
 
 	if (p_lossy)
@@ -655,7 +655,8 @@ static int exfat_load_upcase_table(struct super_block *sb,
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	unsigned int sect_size = sb->s_blocksize;
-	unsigned int i, index = 0, checksum = 0;
+	unsigned int i, index = 0;
+	u32 chksum = 0;
 	int ret;
 	unsigned char skip = false;
 	unsigned short *upcase_table;
@@ -681,13 +682,6 @@ static int exfat_load_upcase_table(struct super_block *sb,
 		for (i = 0; i < sect_size && index <= 0xFFFF; i += 2) {
 			unsigned short uni = get_unaligned_le16(bh->b_data + i);
 
-			checksum = ((checksum & 1) ? 0x80000000 : 0) +
-				(checksum >> 1) +
-				*(((unsigned char *)bh->b_data) + i);
-			checksum = ((checksum & 1) ? 0x80000000 : 0) +
-				(checksum >> 1) +
-				*(((unsigned char *)bh->b_data) + (i + 1));
-
 			if (skip) {
 				index += uni;
 				skip = false;
@@ -701,13 +695,14 @@ static int exfat_load_upcase_table(struct super_block *sb,
 			}
 		}
 		brelse(bh);
+		chksum = exfat_calc_chksum32(bh->b_data, i, chksum, CS_DEFAULT);
 	}
 
-	if (index >= 0xFFFF && utbl_checksum == checksum)
+	if (index >= 0xFFFF && utbl_checksum == chksum)
 		return 0;
 
 	exfat_err(sb, "failed to load upcase table (idx : 0x%08x, chksum : 0x%08x, utbl_chksum : 0x%08x)",
-		  index, checksum, utbl_checksum);
+		  index, chksum, utbl_checksum);
 	ret = -EINVAL;
 free_table:
 	exfat_free_upcase_table(sbi);
-- 
2.25.1