Commit 4fd5ea43 authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Theodore Ts'o
Browse files

jbd2: checksum journal superblock 



Calculate and verify a checksum covering the journal superblock.

Signed-off-by: default avatarDarrick J. Wong <djwong@us.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 01b5adce

fs/jbd2/journal.c

+47 −0
Original line number Diff line number Diff line
@@ -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 */

include/linux/jbd2.h

+3 −0
Original line number Diff line number Diff line
@@ -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;

};



/*