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Subject[PATCH 1/2] ext4: Calculate and verify inode checksums
This patch introduces to ext4 the ability to calculate and verify inode
checksums. This requires the use of a new ro compatibility flag and some
accompanying e2fsprogs patches to provide the relevant features in tune2fs and
e2fsck.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
fs/ext4/ext4.h | 6 ++++--
fs/ext4/inode.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 55 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 4daaf2b..8815928 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -617,7 +617,7 @@ struct ext4_inode {
} masix2;
} osd2; /* OS dependent 2 */
__le16 i_extra_isize;
- __le16 i_pad1;
+ __le16 i_checksum; /* crc16(sb_uuid+inodenum+inode) */
__le32 i_ctime_extra; /* extra Change time (nsec << 2 | epoch) */
__le32 i_mtime_extra; /* extra Modification time(nsec << 2 | epoch) */
__le32 i_atime_extra; /* extra Access time (nsec << 2 | epoch) */
@@ -1338,6 +1338,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
#define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010
#define EXT4_FEATURE_RO_COMPAT_DIR_NLINK 0x0020
#define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE 0x0040
+#define EXT4_FEATURE_RO_COMPAT_INODE_CSUM 0x0400

#define EXT4_FEATURE_INCOMPAT_COMPRESSION 0x0001
#define EXT4_FEATURE_INCOMPAT_FILETYPE 0x0002
@@ -1364,7 +1365,8 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
EXT4_FEATURE_RO_COMPAT_DIR_NLINK | \
EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE | \
EXT4_FEATURE_RO_COMPAT_BTREE_DIR |\
- EXT4_FEATURE_RO_COMPAT_HUGE_FILE)
+ EXT4_FEATURE_RO_COMPAT_HUGE_FILE |\
+ EXT4_FEATURE_RO_COMPAT_INODE_CSUM)

/*
* Default values for user and/or group using reserved blocks
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1a86282..dc76f19 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -42,6 +42,7 @@
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>
+#include <linux/crc16.h>

#include "ext4_jbd2.h"
#include "xattr.h"
@@ -52,6 +53,40 @@

#define MPAGE_DA_EXTENT_TAIL 0x01

+static __le16 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+ struct ext4_inode_info *ei = EXT4_I(inode);
+ int offset = offsetof(struct ext4_inode, i_checksum);
+ __le32 inum = cpu_to_le32(inode->i_ino);
+ __u16 crc = 0;
+
+ if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_RO_COMPAT_INODE_CSUM) &&
+ le16_to_cpu(raw->i_extra_isize) >= 4) {
+ crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
+ crc = crc16(crc, (__u8 *)&inum, sizeof(inum));
+ crc = crc16(crc, (__u8 *)raw, offset);
+ offset += sizeof(raw->i_checksum); /* skip checksum */
+ /* for checksum of struct ext4_inode do the rest...*/
+ if (ei->i_extra_isize > 4)
+ crc = crc16(crc, (__u8 *)raw + offset,
+ ei->i_extra_isize - 4);
+ }
+
+ return cpu_to_le16(crc);
+}
+
+static int ext4_inode_csum_verify(struct inode *inode, struct ext4_inode *raw)
+{
+ if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_RO_COMPAT_INODE_CSUM) &&
+ (raw->i_checksum != ext4_inode_csum(inode, raw)))
+ return 0;
+
+ return 1;
+}
+
static inline int ext4_begin_ordered_truncate(struct inode *inode,
loff_t new_size)
{
@@ -4802,7 +4837,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
struct ext4_inode *raw_inode;
struct ext4_inode_info *ei;
struct inode *inode;
- journal_t *journal = EXT4_SB(sb)->s_journal;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ journal_t *journal = sbi->s_journal;
long ret;
int block;

@@ -4916,6 +4952,14 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
} else
ei->i_extra_isize = 0;

+ if (!ext4_inode_csum_verify(inode, raw_inode)) {
+ EXT4_ERROR_INODE(inode, "checksum invalid (%u != %u)",
+ le16_to_cpu(ext4_inode_csum(inode, raw_inode)),
+ le16_to_cpu(raw_inode->i_checksum));
+ ret = -EIO;
+ goto bad_inode;
+ }
+
EXT4_INODE_GET_XTIME(i_ctime, inode, raw_inode);
EXT4_INODE_GET_XTIME(i_mtime, inode, raw_inode);
EXT4_INODE_GET_XTIME(i_atime, inode, raw_inode);
@@ -5138,6 +5182,12 @@ static int ext4_do_update_inode(handle_t *handle,
raw_inode->i_version_hi =
cpu_to_le32(inode->i_version >> 32);
raw_inode->i_extra_isize = cpu_to_le16(ei->i_extra_isize);
+
+ if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_RO_COMPAT_INODE_CSUM) &&
+ EXT4_FITS_IN_INODE(raw_inode, ei, i_checksum))
+ raw_inode->i_checksum =
+ ext4_inode_csum(inode, raw_inode);
}

BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");

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