[PATCH 18/47] libext2fs: Verify and calculate extent tree block checksums

["Darrick J. Wong" <djwong@us.ibm.com>]

Verify and calculate extent tree block checksums when processing filesystems.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
 lib/ext2fs/csum.c         |   75 +++++++++++++++++++++++++++++++++++++++++++++
 lib/ext2fs/ext2fs.h       |    6 ++++
 lib/ext2fs/ext3_extents.h |   11 +++++++
 lib/ext2fs/extent.c       |   21 +++++++++++++
 4 files changed, 113 insertions(+), 0 deletions(-)


diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
index 524d0e5..7f2d5af 100644
--- a/lib/ext2fs/csum.c
+++ b/lib/ext2fs/csum.c
@@ -30,6 +30,81 @@
 #define STATIC static
 #endif
 
+#define EXT3_EXTENT_TAIL_OFFSET(hdr)	(sizeof(struct ext3_extent_header) + \
+	(sizeof(struct ext3_extent) * ext2fs_le16_to_cpu((hdr)->eh_max)))
+
+static struct ext3_extent_tail *get_extent_tail(struct ext3_extent_header *h)
+{
+	return (struct ext3_extent_tail *)(((void *)h) +
+					   EXT3_EXTENT_TAIL_OFFSET(h));
+}
+
+static errcode_t ext2fs_extent_block_csum(ext2_filsys fs, ext2_ino_t inum,
+					  struct ext3_extent_header *eh,
+					  __u32 *crc)
+{
+	int size;
+	__u32 ncrc;
+	errcode_t retval = 0;
+
+	size = EXT3_EXTENT_TAIL_OFFSET(eh) + offsetof(struct ext3_extent_tail,
+						      et_checksum);
+
+	inum = ext2fs_cpu_to_le32(inum);
+	ncrc = ext2fs_crc32c_le(~0, fs->super->s_uuid,
+			       sizeof(fs->super->s_uuid));
+	ncrc = ext2fs_crc32c_le(ncrc, (unsigned char *)&inum, sizeof(inum));
+	ncrc = ext2fs_crc32c_le(ncrc, (unsigned char *)eh, size);
+	*crc = ncrc;
+
+	return retval;
+}
+
+int ext2fs_extent_block_csum_verify(ext2_filsys fs, ext2_ino_t inum,
+				    struct ext3_extent_header *eh)
+{
+	errcode_t retval;
+	__u32 provided, calculated;
+	struct ext3_extent_tail *t = get_extent_tail(eh);
+
+	/*
+	 * The extent tree structures are accessed in LE order, so we must
+	 * swap the checksum bytes here.
+	 */
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 1;
+
+	provided = ext2fs_le32_to_cpu(t->et_checksum);
+	retval = ext2fs_extent_block_csum(fs, inum, eh, &calculated);
+	if (retval)
+		return 0;
+
+	return provided == calculated;
+}
+
+errcode_t ext2fs_extent_block_csum_set(ext2_filsys fs, ext2_ino_t inum,
+				       struct ext3_extent_header *eh)
+{
+	errcode_t retval;
+	__u32 crc;
+	struct ext3_extent_tail *t = get_extent_tail(eh);
+
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 0;
+
+	/*
+	 * The extent tree structures are accessed in LE order, so we must
+	 * swap the checksum bytes here.
+	 */
+	retval = ext2fs_extent_block_csum(fs, inum, eh, &crc);
+	if (retval)
+		return retval;
+	t->et_checksum = ext2fs_cpu_to_le32(crc);
+	return retval;
+}
+
 static __u32 ext2fs_bitmap_csum(ext2_filsys fs, dgrp_t group, char *bitmap,
 				int size)
 {
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 3b514a7..bf2a9e0 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -929,6 +929,12 @@ extern __u32 ext2fs_crc32c_be(__u32 crc, unsigned char const *p, size_t len);
 extern __u32 ext2fs_crc32c_le(__u32 crc, unsigned char const *p, size_t len);
 
 /* csum.c */
+extern errcode_t ext2fs_extent_block_csum_set(ext2_filsys fs,
+					      ext2_ino_t inum,
+					      struct ext3_extent_header *eh);
+extern int ext2fs_extent_block_csum_verify(ext2_filsys fs,
+					   ext2_ino_t inum,
+					   struct ext3_extent_header *eh);
 extern errcode_t ext2fs_block_bitmap_csum_set(ext2_filsys fs, dgrp_t group,
 					      char *bitmap, int size);
 extern int ext2fs_block_bitmap_csum_verify(ext2_filsys fs, dgrp_t group,
diff --git a/lib/ext2fs/ext3_extents.h b/lib/ext2fs/ext3_extents.h
index 88fabc9..99a4f47 100644
--- a/lib/ext2fs/ext3_extents.h
+++ b/lib/ext2fs/ext3_extents.h
@@ -19,6 +19,17 @@
  */
 
 /*
+ * This is extent tail on-disk structure.
+ * All other extent structures are 12 bytes long.  It turns out that
+ * block_size % 12 >= 4 for all valid block sizes (1k, 2k, 4k).
+ * Therefore, this tail structure can be crammed into the end of the block
+ * without having to rebalance the tree.
+ */
+struct ext3_extent_tail {
+	__u32	et_checksum;	/* crc32c(uuid+inum+extent_block) */
+};
+
+/*
  * this is extent on-disk structure
  * it's used at the bottom of the tree
  */
diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
index eb096d6..9cb5984 100644
--- a/lib/ext2fs/extent.c
+++ b/lib/ext2fs/extent.c
@@ -455,6 +455,13 @@ retry:
 			return retval;
 		}
 
+		if (!(handle->fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
+		    !ext2fs_extent_block_csum_verify(handle->fs, handle->ino,
+						     eh)) {
+			handle->level--;
+			return EXT2_ET_EXTENT_HEADER_BAD;
+		}
+
 		newpath->left = newpath->entries =
 			ext2fs_le16_to_cpu(eh->eh_entries);
 		newpath->max_entries = ext2fs_le16_to_cpu(eh->eh_max);
@@ -541,6 +548,7 @@ static errcode_t update_path(ext2_extent_handle_t handle)
 	blk64_t				blk;
 	errcode_t			retval;
 	struct ext3_extent_idx		*ix;
+	struct ext3_extent_header	*eh;
 
 	if (handle->level == 0) {
 		retval = ext2fs_write_inode(handle->fs, handle->ino,
@@ -550,6 +558,14 @@ static errcode_t update_path(ext2_extent_handle_t handle)
 		blk = ext2fs_le32_to_cpu(ix->ei_leaf) +
 			((__u64) ext2fs_le16_to_cpu(ix->ei_leaf_hi) << 32);
 
+		/* then update the checksum */
+		eh = (struct ext3_extent_header *)
+				handle->path[handle->level].buf;
+		retval = ext2fs_extent_block_csum_set(handle->fs, handle->ino,
+						      eh);
+		if (retval)
+			return retval;
+
 		retval = io_channel_write_blk64(handle->fs->io,
 				      blk, 1, handle->path[handle->level].buf);
 	}
@@ -958,6 +974,11 @@ static errcode_t extent_node_split(ext2_extent_handle_t handle)
 
 	new_node_start = ext2fs_le32_to_cpu(EXT_FIRST_INDEX(neweh)->ei_block);
 
+	/* then update the checksum */
+	retval = ext2fs_extent_block_csum_set(handle->fs, handle->ino, neweh);
+	if (retval)
+		goto done;
+
 	/* ...and write the new node block out to disk. */
 	retval = io_channel_write_blk64(handle->fs->io, new_node_pblk, 1,
 					block_buf);