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ext4: calculate and verify inode checksums
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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.  The inode generation changes have
been integrated into this patch.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Darrick J. Wong authored and Theodore Ts'o committed Apr 29, 2012
1 parent a9c4731 commit 814525f
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Showing 4 changed files with 126 additions and 8 deletions.
3 changes: 3 additions & 0 deletions fs/ext4/ext4.h
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Original file line number Diff line number Diff line change
Expand Up @@ -915,6 +915,9 @@ struct ext4_inode_info {
*/
tid_t i_sync_tid;
tid_t i_datasync_tid;

/* Precomputed uuid+inum+igen checksum for seeding inode checksums */
__u32 i_csum_seed;
};

/*
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13 changes: 13 additions & 0 deletions fs/ext4/ialloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -850,6 +850,19 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
inode->i_generation = sbi->s_next_generation++;
spin_unlock(&sbi->s_next_gen_lock);

/* Precompute checksum seed for inode metadata */
if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
__u32 csum;
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
__le32 inum = cpu_to_le32(inode->i_ino);
__le32 gen = cpu_to_le32(inode->i_generation);
csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&inum,
sizeof(inum));
ei->i_csum_seed = ext4_chksum(sbi, csum, (__u8 *)&gen,
sizeof(gen));
}

ext4_clear_state_flags(ei); /* Only relevant on 32-bit archs */
ext4_set_inode_state(inode, EXT4_STATE_NEW);

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111 changes: 103 additions & 8 deletions fs/ext4/inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,73 @@

#define MPAGE_DA_EXTENT_TAIL 0x01

static __u32 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw,
struct ext4_inode_info *ei)
{
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
__u16 csum_lo;
__u16 csum_hi = 0;
__u32 csum;

csum_lo = raw->i_checksum_lo;
raw->i_checksum_lo = 0;
if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi)) {
csum_hi = raw->i_checksum_hi;
raw->i_checksum_hi = 0;
}

csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)raw,
EXT4_INODE_SIZE(inode->i_sb));

raw->i_checksum_lo = csum_lo;
if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi))
raw->i_checksum_hi = csum_hi;

return csum;
}

static int ext4_inode_csum_verify(struct inode *inode, struct ext4_inode *raw,
struct ext4_inode_info *ei)
{
__u32 provided, calculated;

if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
cpu_to_le32(EXT4_OS_LINUX) ||
!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
return 1;

provided = le16_to_cpu(raw->i_checksum_lo);
calculated = ext4_inode_csum(inode, raw, ei);
if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi))
provided |= ((__u32)le16_to_cpu(raw->i_checksum_hi)) << 16;
else
calculated &= 0xFFFF;

return provided == calculated;
}

static void ext4_inode_csum_set(struct inode *inode, struct ext4_inode *raw,
struct ext4_inode_info *ei)
{
__u32 csum;

if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
cpu_to_le32(EXT4_OS_LINUX) ||
!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
return;

csum = ext4_inode_csum(inode, raw, ei);
raw->i_checksum_lo = cpu_to_le16(csum & 0xFFFF);
if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi))
raw->i_checksum_hi = cpu_to_le16(csum >> 16);
}

static inline int ext4_begin_ordered_truncate(struct inode *inode,
loff_t new_size)
{
Expand Down Expand Up @@ -3644,6 +3711,39 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
if (ret < 0)
goto bad_inode;
raw_inode = ext4_raw_inode(&iloc);

if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
EXT4_INODE_SIZE(inode->i_sb)) {
EXT4_ERROR_INODE(inode, "bad extra_isize (%u != %u)",
EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize,
EXT4_INODE_SIZE(inode->i_sb));
ret = -EIO;
goto bad_inode;
}
} else
ei->i_extra_isize = 0;

/* Precompute checksum seed for inode metadata */
if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
__u32 csum;
__le32 inum = cpu_to_le32(inode->i_ino);
__le32 gen = raw_inode->i_generation;
csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&inum,
sizeof(inum));
ei->i_csum_seed = ext4_chksum(sbi, csum, (__u8 *)&gen,
sizeof(gen));
}

if (!ext4_inode_csum_verify(inode, raw_inode, ei)) {
EXT4_ERROR_INODE(inode, "checksum invalid");
ret = -EIO;
goto bad_inode;
}

inode->i_mode = le16_to_cpu(raw_inode->i_mode);
inode->i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
inode->i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
Expand Down Expand Up @@ -3721,12 +3821,6 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
}

if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
EXT4_INODE_SIZE(inode->i_sb)) {
ret = -EIO;
goto bad_inode;
}
if (ei->i_extra_isize == 0) {
/* The extra space is currently unused. Use it. */
ei->i_extra_isize = sizeof(struct ext4_inode) -
Expand All @@ -3738,8 +3832,7 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
if (*magic == cpu_to_le32(EXT4_XATTR_MAGIC))
ext4_set_inode_state(inode, EXT4_STATE_XATTR);
}
} else
ei->i_extra_isize = 0;
}

EXT4_INODE_GET_XTIME(i_ctime, inode, raw_inode);
EXT4_INODE_GET_XTIME(i_mtime, inode, raw_inode);
Expand Down Expand Up @@ -3963,6 +4056,8 @@ static int ext4_do_update_inode(handle_t *handle,
raw_inode->i_extra_isize = cpu_to_le16(ei->i_extra_isize);
}

ext4_inode_csum_set(inode, raw_inode, ei);

BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
rc = ext4_handle_dirty_metadata(handle, NULL, bh);
if (!err)
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7 changes: 7 additions & 0 deletions fs/ext4/ioctl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -152,6 +152,13 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
if (!inode_owner_or_capable(inode))
return -EPERM;

if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
ext4_warning(sb, "Setting inode version is not "
"supported with metadata_csum enabled.");
return -ENOTTY;
}

err = mnt_want_write_file(filp);
if (err)
return err;
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