jbd2: checksum descriptor blocks

Calculate and verify a checksum of each descriptor block.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 36 insertions, 1 deletions

diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index 728ecd0..066ee60 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -174,6 +174,25 @@ 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 jbd2_journal_block_tail *tail;
+	__u32 provided, calculated;
+
+	if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		return 1;
+
+	tail = (struct jbd2_journal_block_tail *)(buf + j->j_blocksize -
+			sizeof(struct jbd2_journal_block_tail));
+	provided = tail->t_checksum;
+	tail->t_checksum = 0;
+	calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
+	tail->t_checksum = provided;
+
+	provided = be32_to_cpu(provided);
+	return provided == calculated;
+}
 
 /*
  * Count the number of in-use tags in a journal descriptor block.
@@ -186,6 +205,9 @@ 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 (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		size -= sizeof(struct jbd2_journal_block_tail);
+
 	tagp = &bh->b_data[sizeof(journal_header_t)];
 
 	while ((tagp - bh->b_data + tag_bytes) <= size) {
@@ -366,6 +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;
 
 	/*
 	 * First thing is to establish what we expect to find in the log
@@ -451,6 +474,18 @@ static int do_one_pass(journal_t *journal,
 
 		switch(blocktype) {
 		case JBD2_DESCRIPTOR_BLOCK:
+			/* Verify checksum first */
+			if (JBD2_HAS_INCOMPAT_FEATURE(journal,
+					JBD2_FEATURE_INCOMPAT_CSUM_V2))
+				descr_csum_size =
+					sizeof(struct jbd2_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,
@@ -481,7 +516,7 @@ 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;