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-rw-r--r--fs/ext4/super.c47
1 files changed, 47 insertions, 0 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e2bdf93693a6..dd4ff9c87358 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -37,12 +37,14 @@
#include <linux/quotaops.h>
#include <linux/seq_file.h>
#include <linux/log2.h>
+#include <linux/crc16.h>
#include <asm/uaccess.h>
#include "xattr.h"
#include "acl.h"
#include "namei.h"
+#include "group.h"
static int ext4_load_journal(struct super_block *, struct ext4_super_block *,
unsigned long journal_devnum);
@@ -1308,6 +1310,43 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
return res;
}
+__le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
+ struct ext4_group_desc *gdp)
+{
+ __u16 crc = 0;
+
+ if (sbi->s_es->s_feature_ro_compat &
+ cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+ int offset = offsetof(struct ext4_group_desc, bg_checksum);
+ __le32 le_group = cpu_to_le32(block_group);
+
+ crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
+ crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
+ crc = crc16(crc, (__u8 *)gdp, offset);
+ offset += sizeof(gdp->bg_checksum); /* skip checksum */
+ /* for checksum of struct ext4_group_desc do the rest...*/
+ if ((sbi->s_es->s_feature_incompat &
+ cpu_to_le32(EXT4_FEATURE_INCOMPAT_64BIT)) &&
+ offset < le16_to_cpu(sbi->s_es->s_desc_size))
+ crc = crc16(crc, (__u8 *)gdp + offset,
+ le16_to_cpu(sbi->s_es->s_desc_size) -
+ offset);
+ }
+
+ return cpu_to_le16(crc);
+}
+
+int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 block_group,
+ struct ext4_group_desc *gdp)
+{
+ if ((sbi->s_es->s_feature_ro_compat &
+ cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) &&
+ (gdp->bg_checksum != ext4_group_desc_csum(sbi, block_group, gdp)))
+ return 0;
+
+ return 1;
+}
+
/* Called at mount-time, super-block is locked */
static int ext4_check_descriptors (struct super_block * sb)
{
@@ -1362,6 +1401,14 @@ static int ext4_check_descriptors (struct super_block * sb)
i, inode_table);
return 0;
}
+ if (!ext4_group_desc_csum_verify(sbi, i, gdp)) {
+ ext4_error(sb, __FUNCTION__,
+ "Checksum for group %d failed (%u!=%u)\n", i,
+ le16_to_cpu(ext4_group_desc_csum(sbi, i,
+ gdp)),
+ le16_to_cpu(gdp->bg_checksum));
+ return 0;
+ }
first_block += EXT4_BLOCKS_PER_GROUP(sb);
gdp = (struct ext4_group_desc *)
((__u8 *)gdp + EXT4_DESC_SIZE(sb));
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