[PATCH 18/23] jbd2: Checksum journal superblock

[Darrick J. Wong]

Calculate and verify a checksum covering the journal superblock.

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 fs/jbd2/journal.c    |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/jbd2.h |    3 +++
 2 files changed, 53 insertions(+), 0 deletions(-)


diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 554f899..808654a 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -109,6 +109,34 @@ int jbd2_verify_csum_type(journal_t *j, journal_superblock_t *sb)
 	return sb->s_checksum_type == JBD2_CRC32C_CHKSUM;
 }
 
+static __u32 jbd2_superblock_csum(journal_t *j, journal_superblock_t *sb)
+{
+	__u32 csum, old_csum;
+
+	old_csum = sb->s_checksum;
+	sb->s_checksum = 0;
+	csum = jbd2_chksum(j, ~0, (char *)sb, sizeof(journal_superblock_t));
+	sb->s_checksum = old_csum;
+
+	return cpu_to_be32(csum);
+}
+
+int jbd2_superblock_csum_verify(journal_t *j, journal_superblock_t *sb)
+{
+	if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		return 1;
+
+	return sb->s_checksum == jbd2_superblock_csum(j, sb);
+}
+
+void jbd2_superblock_csum_set(journal_t *j, journal_superblock_t *sb)
+{
+	if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		return;
+
+	sb->s_checksum = jbd2_superblock_csum(j, sb);
+}
+
 /*
  * Helper function used to manage commit timeouts
  */
@@ -1178,6 +1206,7 @@ void jbd2_journal_update_superblock(journal_t *journal, int wait)
 	sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
 	sb->s_start    = cpu_to_be32(journal->j_tail);
 	sb->s_errno    = cpu_to_be32(journal->j_errno);
+	jbd2_superblock_csum_set(journal, sb);
 	read_unlock(&journal->j_state_lock);
 
 	BUFFER_TRACE(bh, "marking dirty");
@@ -1295,6 +1324,17 @@ static int journal_get_superblock(journal_t *journal)
 		}
 	}
 
+	/* Check superblock checksum */
+	if (!jbd2_superblock_csum_verify(journal, sb)) {
+		printk(KERN_ERR "JBD: journal checksum error\n");
+		goto out;
+	}
+
+	/* Precompute checksum seed for all metadata */
+	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		journal->j_csum_seed = jbd2_chksum(journal, ~0, sb->s_uuid,
+						   sizeof(sb->s_uuid));
+
 	set_buffer_verified(bh);
 
 	return 0;
@@ -1581,6 +1621,13 @@ int jbd2_journal_set_features (journal_t *journal, unsigned long compat,
 				return 0;
 			}
 		}
+
+		/* Precompute checksum seed for all metadata */
+		if (JBD2_HAS_INCOMPAT_FEATURE(journal,
+					      JBD2_FEATURE_INCOMPAT_CSUM_V2))
+			journal->j_csum_seed = jbd2_chksum(journal, ~0,
+							   sb->s_uuid,
+							   sizeof(sb->s_uuid));
 	}
 
 	/* If enabling v1 checksums, downgrade superblock */
@@ -1591,6 +1638,7 @@ int jbd2_journal_set_features (journal_t *journal, unsigned long compat,
 	sb->s_feature_compat    |= cpu_to_be32(compat);
 	sb->s_feature_ro_compat |= cpu_to_be32(ro);
 	sb->s_feature_incompat  |= cpu_to_be32(incompat);
+	jbd2_journal_update_superblock(journal, 0);
 
 	return 1;
 #undef COMPAT_FEATURE_ON
@@ -1621,6 +1669,7 @@ void jbd2_journal_clear_features(journal_t *journal, unsigned long compat,
 	sb->s_feature_compat    &= ~cpu_to_be32(compat);
 	sb->s_feature_ro_compat &= ~cpu_to_be32(ro);
 	sb->s_feature_incompat  &= ~cpu_to_be32(incompat);
+	jbd2_journal_update_superblock(journal, 0);
 }
 EXPORT_SYMBOL(jbd2_journal_clear_features);
 
@@ -1669,6 +1718,7 @@ static int journal_convert_superblock_v1(journal_t *journal,
 
 	sb->s_nr_users = cpu_to_be32(1);
 	sb->s_header.h_blocktype = cpu_to_be32(JBD2_SUPERBLOCK_V2);
+	jbd2_superblock_csum_set(journal, sb);
 	journal->j_format_version = 2;
 
 	bh = journal->j_sb_buffer;
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 320de7d..f321226 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -969,6 +969,9 @@ struct journal_s
 
 	/* Reference to checksum algorithm driver via cryptoapi */
 	struct crypto_shash *j_chksum_driver;
+
+	/* Precomputed journal UUID checksum for seeding other checksums */
+	__u32 j_csum_seed;
 };
 
 /*

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