diff mbox series

[3/4] exfat: add boot region verification

Message ID 20200525115052.19243-3-kohada.t2@gmail.com (mailing list archive)
State New, archived
Headers show
Series [1/4] exfat: redefine PBR as boot_sector | expand

Commit Message

Tetsuhiro Kohada May 25, 2020, 11:50 a.m. UTC 
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>
---
 fs/exfat/exfat_fs.h |  1 +
 fs/exfat/misc.c     | 14 +++++++++++++
 fs/exfat/super.c    | 50 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)

Comments

Namjae Jeon May 26, 2020, 7:23 a.m. UTC | #1 
[snip]
> +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_err(sb, "no exboot-signature");
                                exfat_warn(sb, "Invalid exboot-signature(sector = %d): 0x%08x", sn, *p_sig);
> +				brelse(bh);
> +				return -EINVAL;
Don't make mount error, Just print warning message.
> +			}
> +		}
> +
> +		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, "mismatch checksum");
Print invalid checksum value also.
> +			brelse(bh);
> +			return -EINVAL;
> +		}
> +	}
> +	brelse(bh);
> +	return 0;
> +}
> +
>  /* mount the file system volume */
>  static int __exfat_fill_super(struct super_block *sb)  { @@ -498,6 +542,12 @@ 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
kernel test robot May 29, 2020, 4:51 p.m. UTC | #2 
Hi Tetsuhiro,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on next-20200519]
[cannot apply to linus/master v5.7-rc7 v5.7-rc6 v5.7-rc5 v5.7-rc7]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Tetsuhiro-Kohada/exfat-redefine-PBR-as-boot_sector/20200525-195329
base:    fb57b1fabcb28f358901b2df90abd2b48abc1ca8
config: c6x-randconfig-s032-20200529 (attached as .config)
compiler: c6x-elf-gcc (GCC) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.1-243-gc100a7ab-dirty
        # save the attached .config to linux build tree
        make W=1 C=1 ARCH=c6x CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>


sparse warnings: (new ones prefixed by >>)

>> fs/exfat/super.c:485:29: sparse: sparse: cast to restricted __le32
>> fs/exfat/super.c:485:29: sparse: sparse: cast to restricted __le32
>> fs/exfat/super.c:485:29: sparse: sparse: cast to restricted __le32
>> fs/exfat/super.c:485:29: sparse: sparse: cast to restricted __le32
>> fs/exfat/super.c:485:29: sparse: sparse: cast to restricted __le32
>> fs/exfat/super.c:485:29: sparse: sparse: cast to restricted __le32
   fs/exfat/super.c:504:21: sparse: sparse: cast to restricted __le32
   fs/exfat/super.c:504:21: sparse: sparse: cast to restricted __le32
   fs/exfat/super.c:504:21: sparse: sparse: cast to restricted __le32
   fs/exfat/super.c:504:21: sparse: sparse: cast to restricted __le32
   fs/exfat/super.c:504:21: sparse: sparse: cast to restricted __le32
   fs/exfat/super.c:504:21: sparse: sparse: cast to restricted __le32

vim +485 fs/exfat/super.c

   469	
   470	static int exfat_verify_boot_region(struct super_block *sb)
   471	{
   472		struct buffer_head *bh = NULL;
   473		u32 chksum = 0, *p_sig, *p_chksum;
   474		int sn, i;
   475	
   476		/* read boot sector sub-regions */
   477		for (sn = 0; sn < 11; sn++) {
   478			bh = sb_bread(sb, sn);
   479			if (!bh)
   480				return -EIO;
   481	
   482			if (sn != 0 && sn <= 8) {
   483				/* extended boot sector sub-regions */
   484				p_sig = (u32 *)&bh->b_data[sb->s_blocksize - 4];
 > 485				if (le32_to_cpu(*p_sig) != EXBOOT_SIGNATURE) {
   486					exfat_err(sb, "no exboot-signature");
   487					brelse(bh);
   488					return -EINVAL;
   489				}
   490			}
   491	
   492			chksum = exfat_calc_chksum32(bh->b_data, sb->s_blocksize,
   493				chksum, sn ? CS_DEFAULT : CS_BOOT_SECTOR);
   494			brelse(bh);
   495		}
   496	
   497		/* boot checksum sub-regions */
   498		bh = sb_bread(sb, sn);
   499		if (!bh)
   500			return -EIO;
   501	
   502		for (i = 0; i < sb->s_blocksize; i += sizeof(u32)) {
   503			p_chksum = (u32 *)&bh->b_data[i];
   504			if (le32_to_cpu(*p_chksum) != chksum) {
   505				exfat_err(sb, "mismatch checksum");
   506				brelse(bh);
   507				return -EINVAL;
   508			}
   509		}
   510		brelse(bh);
   511		return 0;
   512	}
   513	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff mbox series

Patch

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index b0e5b9afc56c..15817281b3c8 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -517,6 +517,7 @@  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..42b3bd3df020 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -486,6 +486,50 @@  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, *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_err(sb, "no exboot-signature");
+				brelse(bh);
+				return -EINVAL;
+			}
+		}
+
+		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, "mismatch checksum");
+			brelse(bh);
+			return -EINVAL;
+		}
+	}
+	brelse(bh);
+	return 0;
+}
+
 /* mount the file system volume */
 static int __exfat_fill_super(struct super_block *sb)
 {
@@ -498,6 +542,12 @@  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");