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exfat: add boot region verification 

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>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
This commit is contained in:
Tetsuhiro Kohada 2020-05-31 18:30:17 +09:00 committed by Namjae Jeon
parent 33404a1598
commit 476189c0ef
3 changed files with 65 additions and 0 deletions
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1
fs/exfat/exfat_fs.h
View File

@ -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);

14
fs/exfat/misc.c
View File

@ -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);

50
fs/exfat/super.c
View File

@ -491,6 +491,50 @@ 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;
__le32 *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 = (__le32 *)&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 = (__le32 *)&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)
{
@ -503,6 +547,12 @@ 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");