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>

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;
 };
 
 /*

fs/ext4/ialloc.c

@@ -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);
 

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)

fs/ext4/ioctl.c

@@ -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;