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SubjectRe: [PATCH 13/25] ubifs: authentication: Add hashes to index nodes
Date
Am Mittwoch, 4. Juli 2018, 14:41:25 CEST schrieb Sascha Hauer:
> With this patch the hashes over the index nodes stored in the tree node
> cache are written to flash and are checked when read back from flash.
> The hash of the root index node is stored in the master node.
>
> During journal replay the hashes are regenerated from the read nodes
> and stored in the tree node cache. This means the nodes must previously
> be authenticated by other means. This is done in a later patch.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> fs/ubifs/master.c | 3 +++
> fs/ubifs/misc.h | 5 +++--
> fs/ubifs/replay.c | 29 ++++++++++++++++++-----------
> fs/ubifs/tnc.c | 13 +++++++++++++
> fs/ubifs/tnc_commit.c | 26 ++++++++++++++++++++++++++
> fs/ubifs/tnc_misc.c | 16 +++++++++++++++-
> fs/ubifs/ubifs.h | 4 ++++
> 7 files changed, 82 insertions(+), 14 deletions(-)
>

[...]

> diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
> index a47fced47823..a00809d4fe6f 100644
> --- a/fs/ubifs/tnc.c
> +++ b/fs/ubifs/tnc.c
> @@ -488,6 +488,12 @@ static int try_read_node(const struct ubifs_info *c, void *buf, int type,
> if (crc != node_crc)
> return 0;
>
> + err = ubifs_node_check_hash(c, buf, zbr->hash);
> + if (err) {
> + ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs);
> + return 0;
> + }

Hmm, I think a global "hash is bad" handler would be nice to have.
That way we always report in the same way.

Maybe also a new file system specific ioctl to query whether a hash
failure was noticed.

> return 1;
> }
>
> @@ -1713,6 +1719,13 @@ static int validate_data_node(struct ubifs_info *c, void *buf,
> goto out;
> }
>
> + err = ubifs_node_check_hash(c, buf, zbr->hash);
> + if (err) {
> + ubifs_err(c, "hash mismatch on node at LEB %d:%d",
> + zbr->lnum, zbr->offs);
> + return err;
> + }
> +
> len = le32_to_cpu(ch->len);
> if (len != zbr->len) {
> ubifs_err(c, "bad node length %d, expected %d", len, zbr->len);
> diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
> index a9df94ad46a3..3ad78d538885 100644
> --- a/fs/ubifs/tnc_commit.c
> +++ b/fs/ubifs/tnc_commit.c
> @@ -38,6 +38,7 @@ static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx,
> struct ubifs_znode *znode, int lnum, int offs, int len)
> {
> struct ubifs_znode *zp;
> + u8 hash[UBIFS_MAX_HASH_LEN];
> int i, err;
>
> /* Make index node */
> @@ -62,6 +63,7 @@ static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx,
> }
> }
> ubifs_prepare_node(c, idx, len, 0);
> + ubifs_node_calc_hash(c, idx, hash);
>
> znode->lnum = lnum;
> znode->offs = offs;
> @@ -78,10 +80,12 @@ static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx,
> zbr->lnum = lnum;
> zbr->offs = offs;
> zbr->len = len;
> + ubifs_copy_hash(c, hash, zbr->hash);
> } else {
> c->zroot.lnum = lnum;
> c->zroot.offs = offs;
> c->zroot.len = len;
> + ubifs_copy_hash(c, hash, c->zroot.hash);
> }
> c->calc_idx_sz += ALIGN(len, 8);
>
> @@ -647,6 +651,8 @@ static int get_znodes_to_commit(struct ubifs_info *c)
> znode->cnext = c->cnext;
> break;
> }
> + znode->cparent = znode->parent;
> + znode->ciip = znode->iip;
> znode->cnext = cnext;
> znode = cnext;
> cnt += 1;
> @@ -840,6 +846,8 @@ static int write_index(struct ubifs_info *c)
> }
>
> while (1) {
> + u8 hash[UBIFS_MAX_HASH_LEN];
> +
> cond_resched();
>
> znode = cnext;
> @@ -857,6 +865,7 @@ static int write_index(struct ubifs_info *c)
> br->lnum = cpu_to_le32(zbr->lnum);
> br->offs = cpu_to_le32(zbr->offs);
> br->len = cpu_to_le32(zbr->len);
> + ubifs_copy_hash(c, zbr->hash, ubifs_branch_hash(c, br));
> if (!zbr->lnum || !zbr->len) {
> ubifs_err(c, "bad ref in znode");
> ubifs_dump_znode(c, znode);
> @@ -868,6 +877,23 @@ static int write_index(struct ubifs_info *c)
> }
> len = ubifs_idx_node_sz(c, znode->child_cnt);
> ubifs_prepare_node(c, idx, len, 0);
> + ubifs_node_calc_hash(c, idx, hash);
> +
> + mutex_lock(&c->tnc_mutex);

This lock looks correct too me.
Just in case, you did test with lockdep enabled? :-)



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