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.  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>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 5adbce5..ca96401 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -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;
 };
 
 /*

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 409c2ee..8207dfa 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -850,6 +850,19 @@ got:
        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);
 

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8bc21ec..16a6735 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -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)
 {
@@ -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);
@@ -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) -
@@ -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);
@@ -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)

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 6eee255..feba55a 100644 (file)
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -152,6 +152,13 @@ flags_out:
                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;