[PATCH 45/47] e2fsck: Check descriptor block checksum when recovering journal

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

Verify the descriptor block checksum when recovering a journal.

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 e2fsck/recovery.c       |   39 ++++++++++++++++++++++++++++++++++++++-
 lib/ext2fs/kernel-jbd.h |    5 +++++
 2 files changed, 43 insertions(+), 1 deletions(-)


diff --git a/e2fsck/recovery.c b/e2fsck/recovery.c
index 8979193..a192378 100644
--- a/e2fsck/recovery.c
+++ b/e2fsck/recovery.c
@@ -174,6 +174,27 @@ static int jread(struct buffer_head **bhp, journal_t *journal,
 	return 0;
 }
 
+static int jbd2_descr_block_csum_verify(journal_t *j,
+					void *buf)
+{
+	struct journal_block_tail *tail;
+	__u32 provided, calculated;
+
+	if (!JFS_HAS_INCOMPAT_FEATURE(j, JFS_FEATURE_INCOMPAT_CSUM_V2))
+		return 1;
+
+	tail = (struct journal_block_tail *)(buf + j->j_blocksize -
+			sizeof(struct journal_block_tail));
+	provided = tail->t_checksum;
+	tail->t_checksum = 0;
+	calculated = ext2fs_crc32c_le(~0, j->j_superblock->s_uuid,
+				      sizeof(j->j_superblock->s_uuid));
+	calculated = ext2fs_crc32c_le(calculated, buf, j->j_blocksize);
+	tail->t_checksum = provided;
+
+	provided = ext2fs_be32_to_cpu(provided);
+	return provided == calculated;
+}
 
 /*
  * Count the number of in-use tags in a journal descriptor block.
@@ -186,6 +207,9 @@ static int count_tags(journal_t *journal, struct buffer_head *bh)
 	int			nr = 0, size = journal->j_blocksize;
 	int			tag_bytes = journal_tag_bytes(journal);
 
+	if (JFS_HAS_INCOMPAT_FEATURE(journal, JFS_FEATURE_INCOMPAT_CSUM_V2))
+		size -= sizeof(struct journal_block_tail);
+
 	tagp = &bh->b_data[sizeof(journal_header_t)];
 
 	while ((tagp - bh->b_data + tag_bytes) <= size) {
@@ -364,6 +388,7 @@ static int do_one_pass(journal_t *journal,
 	int			blocktype;
 	int			tag_bytes = journal_tag_bytes(journal);
 	__u32			crc32_sum = ~0; /* Transactional Checksums */
+	int			descr_csum_size = 0;
 
 	/* Precompute the maximum metadata descriptors in a descriptor block */
 	int			MAX_BLOCKS_PER_DESC;
@@ -454,6 +479,18 @@ static int do_one_pass(journal_t *journal,
 
 		switch(blocktype) {
 		case JFS_DESCRIPTOR_BLOCK:
+			/* Verify checksum first */
+			if (JFS_HAS_INCOMPAT_FEATURE(journal,
+					JFS_FEATURE_INCOMPAT_CSUM_V2))
+				descr_csum_size =
+					sizeof(struct journal_block_tail);
+			if (descr_csum_size > 0 &&
+			    !jbd2_descr_block_csum_verify(journal,
+							  bh->b_data)) {
+				err = -EIO;
+				goto failed;
+			}
+
 			/* If it is a valid descriptor block, replay it
 			 * in pass REPLAY; if journal_checksums enabled, then
 			 * calculate checksums in PASS_SCAN, otherwise,
@@ -484,7 +521,7 @@ static int do_one_pass(journal_t *journal,
 
 			tagp = &bh->b_data[sizeof(journal_header_t)];
 			while ((tagp - bh->b_data + tag_bytes)
-			       <= journal->j_blocksize) {
+			       <= journal->j_blocksize - descr_csum_size) {
 				unsigned long io_block;
 
 				tag = (journal_block_tag_t *) tagp;
diff --git a/lib/ext2fs/kernel-jbd.h b/lib/ext2fs/kernel-jbd.h
index 187cb38..b79eed5 100644
--- a/lib/ext2fs/kernel-jbd.h
+++ b/lib/ext2fs/kernel-jbd.h
@@ -147,6 +147,11 @@ typedef struct journal_block_tag_s
 #define JBD_TAG_SIZE64 (sizeof(journal_block_tag_t))
 #define JBD_TAG_SIZE32 (8)
 
+/* Tail of descriptor block, for checksumming */
+struct journal_block_tail {
+	__u32		t_checksum;
+};
+
 /*
  * The revoke descriptor: used on disk to describe a series of blocks to
  * be revoked from the log

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