Message-ID: <1901352.nUraZMrBkh@blindfold>
Date:   Mon, 27 Aug 2018 22:48:26 +0200
From:   Richard Weinberger <richard@....at>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     linux-mtd@...ts.infradead.org, David Gstir <david@...ma-star.at>,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/25] ubifs: Add authentication nodes to journal

Am Mittwoch, 4. Juli 2018, 14:41:26 CEST schrieb Sascha Hauer:
> Nodes that are written to flash can only be authenticated through the
> index after the next commit. When a journal replay is necessary the
> nodes are not yet referenced by the index and thus can't be
> authenticated.
> 
> This patch overcomes this situation by creating a hash over all nodes
> beginning from the commit start node over the reference node(s) and
> the buds themselves. From
> time to time we insert authentication nodes. Authentication nodes
> contain a HMAC from the current hash state, so that they can be
> used to authenticate a journal replay up to the point where the
> authentication node is. The hash is continued afterwards
> so that theoretically we would only have to check the HMAC of
> the last authentication node we find.
> 
> Overall we get this picture:
> 
> ,,,,,,,,
> ,......,...........................................
> ,. CS  ,               hash1.----.           hash2.----.
> ,.  |  ,                    .    |hmac            .    |hmac
> ,.  v  ,                    .    v                .    v
> ,.REF#0,-> bud -> bud -> bud.-> auth -> bud -> bud.-> auth ...
> ,..|...,...........................................
> ,  |   ,
> ,  |   ,,,,,,,,,,,,,,,
> .  |            hash3,----.
> ,  |                 ,    |hmac
> ,  v                 ,    v
> , REF#1 -> bud -> bud,-> auth ...
> ,,,|,,,,,,,,,,,,,,,,,,
>    v
>   REF#2 -> ...
>    |
>    V
>   ...
> 
> Note how hash3 covers CS, REF#0 and REF#1 so that it is not possible to
> exchange or skip any reference nodes. Unlike the picture suggests the
> auth nodes themselves are not hashed.
> 
> With this it is possible for an offline attacker to cut each journal
> head or to drop the last reference node(s), but not to skip any journal
> heads or to reorder any operations.
> 
> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> ---
>  fs/ubifs/gc.c      |   3 +-
>  fs/ubifs/journal.c | 110 ++++++++++++++++++++++++++++++++++++++-------
>  fs/ubifs/log.c     |  17 +++++++
>  fs/ubifs/replay.c  |   2 +
>  fs/ubifs/super.c   |  10 +++++
>  fs/ubifs/ubifs.h   |   8 ++++
>  6 files changed, 134 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/ubifs/gc.c b/fs/ubifs/gc.c
> index a03a47cf880d..ac3a3f7c6a6e 100644
> --- a/fs/ubifs/gc.c
> +++ b/fs/ubifs/gc.c
> @@ -254,7 +254,8 @@ static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
>  			     snod->type == UBIFS_DATA_NODE ||
>  			     snod->type == UBIFS_DENT_NODE ||
>  			     snod->type == UBIFS_XENT_NODE ||
> -			     snod->type == UBIFS_TRUN_NODE);
> +			     snod->type == UBIFS_TRUN_NODE ||
> +			     snod->type == UBIFS_AUTH_NODE);
>  
>  		if (snod->type != UBIFS_INO_NODE  &&
>  		    snod->type != UBIFS_DATA_NODE &&
> diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
> index 55b35bc33c31..4fde75623a3f 100644
> --- a/fs/ubifs/journal.c
> +++ b/fs/ubifs/journal.c
> @@ -228,6 +228,32 @@ static int reserve_space(struct ubifs_info *c, int jhead, int len)
>  	return err;
>  }
>  
> +static void ubifs_hash_nodes(struct ubifs_info *c, void *node,
> +			     int len, struct shash_desc *hash)
> +{
> +	int auth_node_size = ubifs_auth_node_sz(c);
> +
> +	while (1) {
> +		const struct ubifs_ch *ch = node;
> +		int nodelen = le32_to_cpu(ch->len);
> +
> +		ubifs_assert(len >= auth_node_size);
> +
> +		if (len == auth_node_size)
> +			break;
> +
> +		ubifs_assert(len > nodelen);
> +		ubifs_assert(ch->magic == cpu_to_le32(UBIFS_NODE_MAGIC));

A malformed UBIFS image can trigger that assert, right?
Please handle this without ubifs_assert() and abort with an error.
ubifs_assert() does not stop execution by default.

> +		ubifs_shash_update(c, hash, (void *)node, nodelen);
> +
> +		node += ALIGN(nodelen, 8);
> +		len -= ALIGN(nodelen, 8);
> +	}
> +
> +	ubifs_prepare_auth_node(c, node, hash);
> +}
> +
>  /**
>   * write_head - write data to a journal head.
>   * @c: UBIFS file-system description object
> @@ -255,6 +281,9 @@ static int write_head(struct ubifs_info *c, int jhead, void *buf, int len,
>  	dbg_jnl("jhead %s, LEB %d:%d, len %d",
>  		dbg_jhead(jhead), *lnum, *offs, len);
>  
> +	if (ubifs_authenticated(c))
> +		ubifs_hash_nodes(c, buf, len, c->jheads[jhead].log_hash);
> +
>  	err = ubifs_wbuf_write_nolock(wbuf, buf, len);
>  	if (err)
>  		return err;
> @@ -542,7 +571,9 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
>  
>  	len = aligned_dlen + aligned_ilen + UBIFS_INO_NODE_SZ;
>  	/* Make sure to also account for extended attributes */
> -	len += host_ui->data_len;
> +	len += ALIGN(host_ui->data_len, 8);

Hmm, this change seems unrelated.
Why do you need an ALIGN now?

> +	len += ubifs_auth_node_sz(c);
>  
>  	dent = kzalloc(len, GFP_NOFS);
>  	if (!dent)
> @@ -603,6 +634,7 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
>  	}
>  	release_head(c, BASEHD);
>  	kfree(dent);
> +	ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));

You have to account it immediately because while a commit you have no longer
a reference to them?
Upon replay you should have since you scan LEBs anyway.

An shouldn't this only get called when the file system is authenticated?
AFAICT ubifs_add_dirt(c, lnum, 0) is not a no-op.

>  	if (deletion) {
>  		if (nm->hash)
> @@ -677,8 +709,9 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
>  			 const union ubifs_key *key, const void *buf, int len)
>  {
>  	struct ubifs_data_node *data;
> -	int err, lnum, offs, compr_type, out_len, compr_len;
> +	int err, lnum, offs, compr_type, out_len, compr_len, auth_len;
>  	int dlen = COMPRESSED_DATA_NODE_BUF_SZ, allocated = 1;
> +	int aligned_dlen;
>  	struct ubifs_inode *ui = ubifs_inode(inode);
>  	bool encrypted = ubifs_crypt_is_encrypted(inode);
>  	u8 hash[UBIFS_MAX_HASH_LEN];
> @@ -690,7 +723,9 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
>  	if (encrypted)
>  		dlen += UBIFS_CIPHER_BLOCK_SIZE;
>  
> -	data = kmalloc(dlen, GFP_NOFS | __GFP_NOWARN);
> +	auth_len = ubifs_auth_node_sz(c);
> +
> +	data = kmalloc(dlen + auth_len, GFP_NOFS | __GFP_NOWARN);
>  	if (!data) {
>  		/*
>  		 * Fall-back to the write reserve buffer. Note, we might be
> @@ -729,15 +764,16 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
>  	}
>  
>  	dlen = UBIFS_DATA_NODE_SZ + out_len;
> +	aligned_dlen = ALIGN(dlen, 8);
>  	data->compr_type = cpu_to_le16(compr_type);
>  
>  	/* Make reservation before allocating sequence numbers */
> -	err = make_reservation(c, DATAHD, dlen);
> +	err = make_reservation(c, DATAHD, aligned_dlen + auth_len);

Okay, now I understand the ALIGN(), ubifs nodes need to be aligned
at an 8 border. Makes sense, _but_ you change this also for the non-authenticated
case.

>  	if (err)
>  		goto out_free;
>  
>  	ubifs_prepare_node(c, data, dlen, 0);
> -	err = write_head(c, DATAHD, data, dlen, &lnum, &offs, 0);
> +	err = write_head(c, DATAHD, data, aligned_dlen + auth_len, &lnum, &offs, 0);
>  	if (err)
>  		goto out_release;
>  
> @@ -745,6 +781,7 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
>  
>  	ubifs_wbuf_add_ino_nolock(&c->jheads[DATAHD].wbuf, key_inum(c, key));
>  	release_head(c, DATAHD);
> +	ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));
>  
>  	err = ubifs_tnc_add(c, key, lnum, offs, dlen, hash);
>  	if (err)
> @@ -784,7 +821,8 @@ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
>  	int err, lnum, offs;
>  	struct ubifs_ino_node *ino;
>  	struct ubifs_inode *ui = ubifs_inode(inode);
> -	int sync = 0, len = UBIFS_INO_NODE_SZ, last_reference = !inode->i_nlink;
> +	int sync = 0, len, ilen = UBIFS_INO_NODE_SZ, last_reference = !inode->i_nlink;
> +	int aligned_ilen;
>  	u8 hash[UBIFS_MAX_HASH_LEN];
>  
>  	dbg_jnl("ino %lu, nlink %u", inode->i_ino, inode->i_nlink);
> @@ -794,9 +832,14 @@ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
>  	 * need to synchronize the write-buffer either.
>  	 */
>  	if (!last_reference) {
> -		len += ui->data_len;
> +		ilen += ui->data_len;
>  		sync = IS_SYNC(inode);
>  	}
> +
> +	aligned_ilen = ALIGN(ilen, 8);
> +
> +	len = aligned_ilen + ubifs_auth_node_sz(c);
> +
>  	ino = kmalloc(len, GFP_NOFS);
>  	if (!ino)
>  		return -ENOMEM;
> @@ -816,17 +859,20 @@ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
>  					  inode->i_ino);
>  	release_head(c, BASEHD);
>  
> +	if (ubifs_authenticated(c))
> +		ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));
> +
>  	if (last_reference) {
>  		err = ubifs_tnc_remove_ino(c, inode->i_ino);
>  		if (err)
>  			goto out_ro;
>  		ubifs_delete_orphan(c, inode->i_ino);
> -		err = ubifs_add_dirt(c, lnum, len);
> +		err = ubifs_add_dirt(c, lnum, ilen);
>  	} else {
>  		union ubifs_key key;
>  
>  		ino_key_init(c, &key, inode->i_ino);
> -		err = ubifs_tnc_add(c, &key, lnum, offs, len, hash);
> +		err = ubifs_tnc_add(c, &key, lnum, offs, ilen, hash);
>  	}
>  	if (err)
>  		goto out_ro;
> @@ -955,6 +1001,8 @@ int ubifs_jnl_xrename(struct ubifs_info *c, const struct inode *fst_dir,
>  	if (twoparents)
>  		len += plen;
>  
> +	len += ubifs_auth_node_sz(c);
> +
>  	dent1 = kzalloc(len, GFP_NOFS);
>  	if (!dent1)
>  		return -ENOMEM;
> @@ -1014,6 +1062,9 @@ int ubifs_jnl_xrename(struct ubifs_info *c, const struct inode *fst_dir,
>  	}
>  	release_head(c, BASEHD);
>  
> +	if (ubifs_authenticated(c))
> +		ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));
> +
>  	dent_key_init(c, &key, snd_dir->i_ino, snd_nm);
>  	err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen1, hash_dent1, snd_nm);
>  	if (err)
> @@ -1115,6 +1166,9 @@ int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
>  	len = aligned_dlen1 + aligned_dlen2 + ALIGN(ilen, 8) + ALIGN(plen, 8);
>  	if (move)
>  		len += plen;
> +
> +	len += ubifs_auth_node_sz(c);
> +
>  	dent = kzalloc(len, GFP_NOFS);
>  	if (!dent)
>  		return -ENOMEM;
> @@ -1198,6 +1252,9 @@ int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
>  	}
>  	release_head(c, BASEHD);
>  
> +	if (ubifs_authenticated(c))
> +		ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));

This is always the same pattern. How about adding a helper function?
ubifs_add_auth_dirt()?

>  	dent_key_init(c, &key, new_dir->i_ino, new_nm);
>  	err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen1, hash_dent1, new_nm);
>  	if (err)
> @@ -1356,6 +1413,7 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
>  	struct ubifs_trun_node *trun;
>  	struct ubifs_data_node *uninitialized_var(dn);
>  	int err, dlen, len, lnum, offs, bit, sz, sync = IS_SYNC(inode);
> +	int aligned_dlen;
>  	struct ubifs_inode *ui = ubifs_inode(inode);
>  	ino_t inum = inode->i_ino;
>  	unsigned int blk;
> @@ -1370,6 +1428,9 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
>  
>  	sz = UBIFS_TRUN_NODE_SZ + UBIFS_INO_NODE_SZ +
>  	     UBIFS_MAX_DATA_NODE_SZ * WORST_COMPR_FACTOR;
> +
> +	sz += ubifs_auth_node_sz(c);
> +
>  	ino = kmalloc(sz, GFP_NOFS);
>  	if (!ino)
>  		return -ENOMEM;
> @@ -1404,10 +1465,15 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
>  		}
>  	}
>  
> +	aligned_dlen = ALIGN(dlen, 8);
> +
>  	/* Must make reservation before allocating sequence numbers */
>  	len = UBIFS_TRUN_NODE_SZ + UBIFS_INO_NODE_SZ;
>  	if (dlen)
> -		len += dlen;
> +		len += aligned_dlen;
> +
> +	len += ubifs_auth_node_sz(c);
> +
>  	err = make_reservation(c, BASEHD, len);
>  	if (err)
>  		goto out_free;
> @@ -1428,6 +1494,9 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
>  		ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf, inum);
>  	release_head(c, BASEHD);
>  
> +	if (ubifs_authenticated(c))
> +		ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));
> +
>  	if (dlen) {
>  		sz = offs + UBIFS_INO_NODE_SZ + UBIFS_TRUN_NODE_SZ;
>  		err = ubifs_tnc_add(c, &key, lnum, sz, dlen, hash_dn);
> @@ -1491,7 +1560,7 @@ int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
>  			   const struct inode *inode,
>  			   const struct fscrypt_name *nm)
>  {
> -	int err, xlen, hlen, len, lnum, xent_offs, aligned_xlen;
> +	int err, xlen, hlen, len, lnum, xent_offs, aligned_xlen, tlen;
>  	struct ubifs_dent_node *xent;
>  	struct ubifs_ino_node *ino;
>  	union ubifs_key xent_key, key1, key2;
> @@ -1511,12 +1580,14 @@ int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
>  	hlen = host_ui->data_len + UBIFS_INO_NODE_SZ;
>  	len = aligned_xlen + UBIFS_INO_NODE_SZ + ALIGN(hlen, 8);
>  
> -	xent = kzalloc(len, GFP_NOFS);
> +	tlen = len + ubifs_auth_node_sz(c);

xlen, hlen, len, tlen, oh my.. ;-)
What does the "t" stand for?
Sorry, I'm very bad at naming things.

> +	xent = kzalloc(tlen, GFP_NOFS);
>  	if (!xent)
>  		return -ENOMEM;
>  
>  	/* Make reservation before allocating sequence numbers */
> -	err = make_reservation(c, BASEHD, len);
> +	err = make_reservation(c, BASEHD, tlen);
>  	if (err) {
>  		kfree(xent);
>  		return err;
> @@ -1539,10 +1610,13 @@ int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
>  	pack_inode(c, ino, host, 1);
>  	ubifs_node_calc_hash(c, ino, hash);
>  
> -	err = write_head(c, BASEHD, xent, len, &lnum, &xent_offs, sync);
> +	err = write_head(c, BASEHD, xent, tlen, &lnum, &xent_offs, sync);
>  	if (!sync && !err)
>  		ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf, host->i_ino);
>  	release_head(c, BASEHD);
> +
> +	if (ubifs_authenticated(c))
> +		ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));
>  	kfree(xent);
>  	if (err)
>  		goto out_ro;
> @@ -1605,6 +1679,7 @@ int ubifs_jnl_change_xattr(struct ubifs_info *c, const struct inode *inode,
>  {
>  	int err, len1, len2, aligned_len, aligned_len1, lnum, offs;
>  	struct ubifs_inode *host_ui = ubifs_inode(host);
> +	struct ubifs_inode *ui = ubifs_inode(inode);
>  	struct ubifs_ino_node *ino;
>  	union ubifs_key key;
>  	int sync = IS_DIRSYNC(host);
> @@ -1617,10 +1692,12 @@ int ubifs_jnl_change_xattr(struct ubifs_info *c, const struct inode *inode,
>  	ubifs_assert(mutex_is_locked(&host_ui->ui_mutex));
>  
>  	len1 = UBIFS_INO_NODE_SZ + host_ui->data_len;
> -	len2 = UBIFS_INO_NODE_SZ + ubifs_inode(inode)->data_len;
> +	len2 = UBIFS_INO_NODE_SZ + ui->data_len;

Why do we need this change, seems unrelated?

>  	aligned_len1 = ALIGN(len1, 8);
>  	aligned_len = aligned_len1 + ALIGN(len2, 8);
>  
> +	aligned_len += ubifs_auth_node_sz(c);
> +
>  	ino = kzalloc(aligned_len, GFP_NOFS);
>  	if (!ino)
>  		return -ENOMEM;
> @@ -1646,6 +1723,9 @@ int ubifs_jnl_change_xattr(struct ubifs_info *c, const struct inode *inode,
>  	if (err)
>  		goto out_ro;
>  
> +	if (ubifs_authenticated(c))
> +		ubifs_add_dirt(c, lnum, ubifs_auth_node_sz(c));
> +
>  	ino_key_init(c, &key, host->i_ino);
>  	err = ubifs_tnc_add(c, &key, lnum, offs, len1, hash_host);
>  	if (err)
> diff --git a/fs/ubifs/log.c b/fs/ubifs/log.c
> index 7cffa120a750..311757b2dc1a 100644
> --- a/fs/ubifs/log.c
> +++ b/fs/ubifs/log.c
> @@ -236,6 +236,7 @@ int ubifs_add_bud_to_log(struct ubifs_info *c, int jhead, int lnum, int offs)
>  	bud->lnum = lnum;
>  	bud->start = offs;
>  	bud->jhead = jhead;
> +	bud->log_hash = NULL;
>  
>  	ref->ch.node_type = UBIFS_REF_NODE;
>  	ref->lnum = cpu_to_le32(bud->lnum);
> @@ -275,6 +276,12 @@ int ubifs_add_bud_to_log(struct ubifs_info *c, int jhead, int lnum, int offs)
>  	if (err)
>  		goto out_unlock;
>  
> +	ubifs_shash_update(c, c->log_hash, (void *)ref, UBIFS_REF_NODE_SZ);
> +
> +	err = ubifs_shash_copy_state(c, c->log_hash, c->jheads[jhead].log_hash);
> +	if (err)
> +		goto out_unlock;
> +
>  	c->lhead_offs += c->ref_node_alsz;
>  
>  	ubifs_add_bud(c, bud);
> @@ -377,6 +384,11 @@ int ubifs_log_start_commit(struct ubifs_info *c, int *ltail_lnum)
>  	cs->cmt_no = cpu_to_le64(c->cmt_no);
>  	ubifs_prepare_node(c, cs, UBIFS_CS_NODE_SZ, 0);
>  
> +	if (c->authenticated) {

ubifs_authenticated(c)?

> +		crypto_shash_init(c->log_hash);
> +		crypto_shash_update(c->log_hash, (void *)cs, UBIFS_CS_NODE_SZ);
> +	}
> +
>  	/*
>  	 * Note, we do not lock 'c->log_mutex' because this is the commit start
>  	 * phase and we are exclusively using the log. And we do not lock
> @@ -402,6 +414,10 @@ int ubifs_log_start_commit(struct ubifs_info *c, int *ltail_lnum)
>  
>  		ubifs_prepare_node(c, ref, UBIFS_REF_NODE_SZ, 0);
>  		len += UBIFS_REF_NODE_SZ;
> +
> +		ubifs_shash_update(c, c->log_hash, (void *)ref,

Why the void * cast?
(Applies to multiple calls to ubifs_shash_update)

> +				   UBIFS_REF_NODE_SZ);
> +		ubifs_shash_copy_state(c, c->log_hash, c->jheads[i].log_hash);
>  	}
>  
>  	ubifs_pad(c, buf + len, ALIGN(len, c->min_io_size) - len);
> @@ -516,6 +532,7 @@ int ubifs_log_post_commit(struct ubifs_info *c, int old_ltail_lnum)
>  		if (err)
>  			return err;
>  		list_del(&bud->list);
> +		kfree(bud->log_hash);
>  		kfree(bud);
>  	}
>  	mutex_lock(&c->log_mutex);
> diff --git a/fs/ubifs/replay.c b/fs/ubifs/replay.c
> index 9e9ff753515f..07a66ae90e89 100644
> --- a/fs/ubifs/replay.c
> +++ b/fs/ubifs/replay.c
> @@ -665,6 +665,8 @@ static int replay_bud(struct ubifs_info *c, struct bud_entry *b)
>  					  old_size, new_size);
>  			break;
>  		}
> +		case UBIFS_AUTH_NODE:
> +			break;
>  		default:
>  			ubifs_err(c, "unexpected node type %d in bud LEB %d:%d",
>  				  snod->type, lnum, snod->offs);
> diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
> index 6b2d80391111..49de06921427 100644
> --- a/fs/ubifs/super.c
> +++ b/fs/ubifs/super.c
> @@ -815,6 +815,9 @@ static int alloc_wbufs(struct ubifs_info *c)
>  		c->jheads[i].wbuf.sync_callback = &bud_wbuf_callback;
>  		c->jheads[i].wbuf.jhead = i;
>  		c->jheads[i].grouped = 1;
> +		c->jheads[i].log_hash = ubifs_hash_get_desc(c);
> +		if (IS_ERR(c->jheads[i].log_hash))
> +			goto out;
>  	}
>  
>  	/*
> @@ -825,6 +828,12 @@ static int alloc_wbufs(struct ubifs_info *c)
>  	c->jheads[GCHD].grouped = 0;
>  
>  	return 0;
> +
> +out:
> +	while (i--)
> +		kfree(c->jheads[i].log_hash);
> +
> +	return err;
>  }
>  
>  /**
> @@ -839,6 +848,7 @@ static void free_wbufs(struct ubifs_info *c)
>  		for (i = 0; i < c->jhead_cnt; i++) {
>  			kfree(c->jheads[i].wbuf.buf);
>  			kfree(c->jheads[i].wbuf.inodes);
> +			kfree(c->jheads[i].log_hash);
>  		}
>  		kfree(c->jheads);
>  		c->jheads = NULL;
> diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
> index bf4a99d799a1..5390d087da3a 100644
> --- a/fs/ubifs/ubifs.h
> +++ b/fs/ubifs/ubifs.h
> @@ -697,6 +697,7 @@ struct ubifs_wbuf {
>   * @jhead: journal head number this bud belongs to
>   * @list: link in the list buds belonging to the same journal head
>   * @rb: link in the tree of all buds
> + * @log_hash: the log hash from the commit start node up to this bud
>   */
>  struct ubifs_bud {
>  	int lnum;
> @@ -704,6 +705,7 @@ struct ubifs_bud {
>  	int jhead;
>  	struct list_head list;
>  	struct rb_node rb;
> +	struct shash_desc *log_hash;
>  };
>  
>  /**
> @@ -711,6 +713,7 @@ struct ubifs_bud {
>   * @wbuf: head's write-buffer
>   * @buds_list: list of bud LEBs belonging to this journal head
>   * @grouped: non-zero if UBIFS groups nodes when writing to this journal head
> + * @log_hash: the log hash from the commit start node up to this journal head
>   *
>   * Note, the @buds list is protected by the @c->buds_lock.
>   */
> @@ -718,6 +721,7 @@ struct ubifs_jhead {
>  	struct ubifs_wbuf wbuf;
>  	struct list_head buds_list;
>  	unsigned int grouped:1;
> +	struct shash_desc *log_hash;
>  };
>  
>  /**
> @@ -1215,6 +1219,8 @@ struct ubifs_debug_info;
>   * @auth_key_name: the authentication key name
>   * @auth_hash_name: the name of the hash algorithm used for authentication
>   * @auth_hash_algo: the authentication hash used for this fs
> + * @log_hash: the log hash from the commit start node up to the latest reference
> + *            node.
>   *
>   * @empty: %1 if the UBI device is empty
>   * @need_recovery: %1 if the file-system needs recovery
> @@ -1456,6 +1462,8 @@ struct ubifs_info {
>  	char *auth_hash_name;
>  	enum hash_algo auth_hash_algo;
>  
> +	struct shash_desc *log_hash;
> +
>  	/* The below fields are used only during mounting and re-mounting */
>  	unsigned int empty:1;
>  	unsigned int need_recovery:1;
> 

Thanks,
//richard

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