From 476189c0ef3b658de3f6b89fd0fdeb6dc451b564 Mon Sep 17 00:00:00 2001 From: Tetsuhiro Kohada Date: Sun, 31 May 2020 18:30:17 +0900 Subject: 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 Reviewed-by: Sungjong Seo Signed-off-by: Namjae Jeon --- fs/exfat/exfat_fs.h | 1 + fs/exfat/misc.c | 14 ++++++++++++++ fs/exfat/super.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 65 insertions(+) (limited to 'fs/exfat') diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index 911f58b93f3d..8c2a70bfaa10 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 6a1330be5a9a..405717e4e3ea 100644 --- a/fs/exfat/super.c +++ b/fs/exfat/super.c @@ -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"); -- cgit v1.2.3-58-ga151