jbd2: checksum journal superblock

Calculate and verify a checksum covering the journal superblock.

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

2 files changed, 50 insertions, 0 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index f04ab6c4b428..9072f03d30b5 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -106,6 +106,34 @@ 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
  */
@@ -1357,6 +1385,7 @@ static void jbd2_journal_update_sb_errno(journal_t *journal)
         jbd_debug(1, "JBD2: updating superblock error (errno %d)\n",
                   journal->j_errno);
         sb->s_errno    = cpu_to_be32(journal->j_errno);
+        jbd2_superblock_csum_set(journal, sb);
         read_unlock(&journal->j_state_lock);
 
         jbd2_write_superblock(journal, WRITE_SYNC);
@@ -1449,6 +1478,17 @@ 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;
@@ -1732,6 +1772,13 @@ 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 */
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 71e77dddebf1..a9632bc55d97 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;
 };
 
 /*