[PATCH] ext3 avoid writing kernel memory to disk

From: Marc-Christian Petersen <m.c.p@kernel.linux-systeme.com>

Solar Designer discovered an information leak in the ext3 code of Linux.
In a worst case an attacker could read sensitive data such as cryptographic
keys which would otherwise never hit disk media.  Theodore Ts'o developed a
correction for this.

fs/jbd/journal.c

@@ -599,6 +599,7 @@ struct journal_head * journal_get_descriptor_buffer(journal_t *journal)
 		return NULL;
 
 	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
+	memset(bh->b_data, 0, journal->j_blocksize);
 	bh->b_state |= (1 << BH_Dirty);
 	BUFFER_TRACE(bh, "return this buffer");
 	return journal_add_journal_head(bh);