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Subject[PATCH v7] drbd: Convert from ahash to shash
In preparing to remove all stack VLA usage from the kernel[1], this
removes the discouraged use of AHASH_REQUEST_ON_STACK in favor of
the smaller SHASH_DESC_ON_STACK by converting from ahash-wrapped-shash
to direct shash. By removing a layer of indirection this both improves
performance and reduces stack usage. The stack allocation will be made
a fixed size in a later patch to the crypto subsystem.

The bulk of the lines in this change are simple s/ahash/shash/, but the
main logic differences are in drbd_csum_ee() and drbd_csum_bio(), which
externalizes the page walking with k(un)map_atomic() instead of using
scattergather.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
---
I'm calling this "v7" just for general sanity over the naming of the
patch when it was part of the large crypto series of changes. Really,
it's v2.

v7: use kmap for possible highmem page addresses (Lars).
---
drivers/block/drbd/drbd_int.h | 13 +++---
drivers/block/drbd/drbd_main.c | 14 +++----
drivers/block/drbd/drbd_nl.c | 39 ++++++------------
drivers/block/drbd/drbd_receiver.c | 35 +++++++++--------
drivers/block/drbd/drbd_worker.c | 63 +++++++++++++++---------------
5 files changed, 76 insertions(+), 88 deletions(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index bc4ed2ed40a2..97d8e290c2be 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -726,10 +726,10 @@ struct drbd_connection {
struct list_head transfer_log; /* all requests not yet fully processed */

struct crypto_shash *cram_hmac_tfm;
- struct crypto_ahash *integrity_tfm; /* checksums we compute, updates protected by connection->data->mutex */
- struct crypto_ahash *peer_integrity_tfm; /* checksums we verify, only accessed from receiver thread */
- struct crypto_ahash *csums_tfm;
- struct crypto_ahash *verify_tfm;
+ struct crypto_shash *integrity_tfm; /* checksums we compute, updates protected by connection->data->mutex */
+ struct crypto_shash *peer_integrity_tfm; /* checksums we verify, only accessed from receiver thread */
+ struct crypto_shash *csums_tfm;
+ struct crypto_shash *verify_tfm;
void *int_dig_in;
void *int_dig_vv;

@@ -1533,8 +1533,9 @@ static inline void ov_out_of_sync_print(struct drbd_device *device)
}


-extern void drbd_csum_bio(struct crypto_ahash *, struct bio *, void *);
-extern void drbd_csum_ee(struct crypto_ahash *, struct drbd_peer_request *, void *);
+extern void drbd_csum_bio(struct crypto_shash *, struct bio *, void *);
+extern void drbd_csum_ee(struct crypto_shash *, struct drbd_peer_request *,
+ void *);
/* worker callbacks */
extern int w_e_end_data_req(struct drbd_work *, int);
extern int w_e_end_rsdata_req(struct drbd_work *, int);
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index a80809bd3057..ccb54791d39c 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1377,7 +1377,7 @@ void drbd_send_ack_dp(struct drbd_peer_device *peer_device, enum drbd_packet cmd
struct p_data *dp, int data_size)
{
if (peer_device->connection->peer_integrity_tfm)
- data_size -= crypto_ahash_digestsize(peer_device->connection->peer_integrity_tfm);
+ data_size -= crypto_shash_digestsize(peer_device->connection->peer_integrity_tfm);
_drbd_send_ack(peer_device, cmd, dp->sector, cpu_to_be32(data_size),
dp->block_id);
}
@@ -1690,7 +1690,7 @@ int drbd_send_dblock(struct drbd_peer_device *peer_device, struct drbd_request *
sock = &peer_device->connection->data;
p = drbd_prepare_command(peer_device, sock);
digest_size = peer_device->connection->integrity_tfm ?
- crypto_ahash_digestsize(peer_device->connection->integrity_tfm) : 0;
+ crypto_shash_digestsize(peer_device->connection->integrity_tfm) : 0;

if (!p)
return -EIO;
@@ -1796,7 +1796,7 @@ int drbd_send_block(struct drbd_peer_device *peer_device, enum drbd_packet cmd,
p = drbd_prepare_command(peer_device, sock);

digest_size = peer_device->connection->integrity_tfm ?
- crypto_ahash_digestsize(peer_device->connection->integrity_tfm) : 0;
+ crypto_shash_digestsize(peer_device->connection->integrity_tfm) : 0;

if (!p)
return -EIO;
@@ -2561,11 +2561,11 @@ void conn_free_crypto(struct drbd_connection *connection)
{
drbd_free_sock(connection);

- crypto_free_ahash(connection->csums_tfm);
- crypto_free_ahash(connection->verify_tfm);
+ crypto_free_shash(connection->csums_tfm);
+ crypto_free_shash(connection->verify_tfm);
crypto_free_shash(connection->cram_hmac_tfm);
- crypto_free_ahash(connection->integrity_tfm);
- crypto_free_ahash(connection->peer_integrity_tfm);
+ crypto_free_shash(connection->integrity_tfm);
+ crypto_free_shash(connection->peer_integrity_tfm);
kfree(connection->int_dig_in);
kfree(connection->int_dig_vv);

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index b4f02768ba47..d15703b1ffe8 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -2303,10 +2303,10 @@ check_net_options(struct drbd_connection *connection, struct net_conf *new_net_c
}

struct crypto {
- struct crypto_ahash *verify_tfm;
- struct crypto_ahash *csums_tfm;
+ struct crypto_shash *verify_tfm;
+ struct crypto_shash *csums_tfm;
struct crypto_shash *cram_hmac_tfm;
- struct crypto_ahash *integrity_tfm;
+ struct crypto_shash *integrity_tfm;
};

static int
@@ -2324,36 +2324,21 @@ alloc_shash(struct crypto_shash **tfm, char *tfm_name, int err_alg)
return NO_ERROR;
}

-static int
-alloc_ahash(struct crypto_ahash **tfm, char *tfm_name, int err_alg)
-{
- if (!tfm_name[0])
- return NO_ERROR;
-
- *tfm = crypto_alloc_ahash(tfm_name, 0, CRYPTO_ALG_ASYNC);
- if (IS_ERR(*tfm)) {
- *tfm = NULL;
- return err_alg;
- }
-
- return NO_ERROR;
-}
-
static enum drbd_ret_code
alloc_crypto(struct crypto *crypto, struct net_conf *new_net_conf)
{
char hmac_name[CRYPTO_MAX_ALG_NAME];
enum drbd_ret_code rv;

- rv = alloc_ahash(&crypto->csums_tfm, new_net_conf->csums_alg,
+ rv = alloc_shash(&crypto->csums_tfm, new_net_conf->csums_alg,
ERR_CSUMS_ALG);
if (rv != NO_ERROR)
return rv;
- rv = alloc_ahash(&crypto->verify_tfm, new_net_conf->verify_alg,
+ rv = alloc_shash(&crypto->verify_tfm, new_net_conf->verify_alg,
ERR_VERIFY_ALG);
if (rv != NO_ERROR)
return rv;
- rv = alloc_ahash(&crypto->integrity_tfm, new_net_conf->integrity_alg,
+ rv = alloc_shash(&crypto->integrity_tfm, new_net_conf->integrity_alg,
ERR_INTEGRITY_ALG);
if (rv != NO_ERROR)
return rv;
@@ -2371,9 +2356,9 @@ alloc_crypto(struct crypto *crypto, struct net_conf *new_net_conf)
static void free_crypto(struct crypto *crypto)
{
crypto_free_shash(crypto->cram_hmac_tfm);
- crypto_free_ahash(crypto->integrity_tfm);
- crypto_free_ahash(crypto->csums_tfm);
- crypto_free_ahash(crypto->verify_tfm);
+ crypto_free_shash(crypto->integrity_tfm);
+ crypto_free_shash(crypto->csums_tfm);
+ crypto_free_shash(crypto->verify_tfm);
}

int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
@@ -2450,17 +2435,17 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
rcu_assign_pointer(connection->net_conf, new_net_conf);

if (!rsr) {
- crypto_free_ahash(connection->csums_tfm);
+ crypto_free_shash(connection->csums_tfm);
connection->csums_tfm = crypto.csums_tfm;
crypto.csums_tfm = NULL;
}
if (!ovr) {
- crypto_free_ahash(connection->verify_tfm);
+ crypto_free_shash(connection->verify_tfm);
connection->verify_tfm = crypto.verify_tfm;
crypto.verify_tfm = NULL;
}

- crypto_free_ahash(connection->integrity_tfm);
+ crypto_free_shash(connection->integrity_tfm);
connection->integrity_tfm = crypto.integrity_tfm;
if (connection->cstate >= C_WF_REPORT_PARAMS && connection->agreed_pro_version >= 100)
/* Do this without trying to take connection->data.mutex again. */
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index be9450f5ad1c..76243e9ef277 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1732,7 +1732,7 @@ static int receive_Barrier(struct drbd_connection *connection, struct packet_inf
}

/* quick wrapper in case payload size != request_size (write same) */
-static void drbd_csum_ee_size(struct crypto_ahash *h,
+static void drbd_csum_ee_size(struct crypto_shash *h,
struct drbd_peer_request *r, void *d,
unsigned int payload_size)
{
@@ -1769,7 +1769,7 @@ read_in_block(struct drbd_peer_device *peer_device, u64 id, sector_t sector,

digest_size = 0;
if (!trim && peer_device->connection->peer_integrity_tfm) {
- digest_size = crypto_ahash_digestsize(peer_device->connection->peer_integrity_tfm);
+ digest_size = crypto_shash_digestsize(peer_device->connection->peer_integrity_tfm);
/*
* FIXME: Receive the incoming digest into the receive buffer
* here, together with its struct p_data?
@@ -1905,7 +1905,7 @@ static int recv_dless_read(struct drbd_peer_device *peer_device, struct drbd_req

digest_size = 0;
if (peer_device->connection->peer_integrity_tfm) {
- digest_size = crypto_ahash_digestsize(peer_device->connection->peer_integrity_tfm);
+ digest_size = crypto_shash_digestsize(peer_device->connection->peer_integrity_tfm);
err = drbd_recv_all_warn(peer_device->connection, dig_in, digest_size);
if (err)
return err;
@@ -3540,7 +3540,7 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
int p_proto, p_discard_my_data, p_two_primaries, cf;
struct net_conf *nc, *old_net_conf, *new_net_conf = NULL;
char integrity_alg[SHARED_SECRET_MAX] = "";
- struct crypto_ahash *peer_integrity_tfm = NULL;
+ struct crypto_shash *peer_integrity_tfm = NULL;
void *int_dig_in = NULL, *int_dig_vv = NULL;

p_proto = be32_to_cpu(p->protocol);
@@ -3621,7 +3621,7 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
* change.
*/

- peer_integrity_tfm = crypto_alloc_ahash(integrity_alg, 0, CRYPTO_ALG_ASYNC);
+ peer_integrity_tfm = crypto_alloc_shash(integrity_alg, 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(peer_integrity_tfm)) {
peer_integrity_tfm = NULL;
drbd_err(connection, "peer data-integrity-alg %s not supported\n",
@@ -3629,7 +3629,7 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
goto disconnect;
}

- hash_size = crypto_ahash_digestsize(peer_integrity_tfm);
+ hash_size = crypto_shash_digestsize(peer_integrity_tfm);
int_dig_in = kmalloc(hash_size, GFP_KERNEL);
int_dig_vv = kmalloc(hash_size, GFP_KERNEL);
if (!(int_dig_in && int_dig_vv)) {
@@ -3659,7 +3659,7 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
mutex_unlock(&connection->resource->conf_update);
mutex_unlock(&connection->data.mutex);

- crypto_free_ahash(connection->peer_integrity_tfm);
+ crypto_free_shash(connection->peer_integrity_tfm);
kfree(connection->int_dig_in);
kfree(connection->int_dig_vv);
connection->peer_integrity_tfm = peer_integrity_tfm;
@@ -3677,7 +3677,7 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
disconnect_rcu_unlock:
rcu_read_unlock();
disconnect:
- crypto_free_ahash(peer_integrity_tfm);
+ crypto_free_shash(peer_integrity_tfm);
kfree(int_dig_in);
kfree(int_dig_vv);
conn_request_state(connection, NS(conn, C_DISCONNECTING), CS_HARD);
@@ -3689,15 +3689,16 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
* return: NULL (alg name was "")
* ERR_PTR(error) if something goes wrong
* or the crypto hash ptr, if it worked out ok. */
-static struct crypto_ahash *drbd_crypto_alloc_digest_safe(const struct drbd_device *device,
+static struct crypto_shash *drbd_crypto_alloc_digest_safe(
+ const struct drbd_device *device,
const char *alg, const char *name)
{
- struct crypto_ahash *tfm;
+ struct crypto_shash *tfm;

if (!alg[0])
return NULL;

- tfm = crypto_alloc_ahash(alg, 0, CRYPTO_ALG_ASYNC);
+ tfm = crypto_alloc_shash(alg, 0, 0);
if (IS_ERR(tfm)) {
drbd_err(device, "Can not allocate \"%s\" as %s (reason: %ld)\n",
alg, name, PTR_ERR(tfm));
@@ -3750,8 +3751,8 @@ static int receive_SyncParam(struct drbd_connection *connection, struct packet_i
struct drbd_device *device;
struct p_rs_param_95 *p;
unsigned int header_size, data_size, exp_max_sz;
- struct crypto_ahash *verify_tfm = NULL;
- struct crypto_ahash *csums_tfm = NULL;
+ struct crypto_shash *verify_tfm = NULL;
+ struct crypto_shash *csums_tfm = NULL;
struct net_conf *old_net_conf, *new_net_conf = NULL;
struct disk_conf *old_disk_conf = NULL, *new_disk_conf = NULL;
const int apv = connection->agreed_pro_version;
@@ -3898,14 +3899,14 @@ static int receive_SyncParam(struct drbd_connection *connection, struct packet_i
if (verify_tfm) {
strcpy(new_net_conf->verify_alg, p->verify_alg);
new_net_conf->verify_alg_len = strlen(p->verify_alg) + 1;
- crypto_free_ahash(peer_device->connection->verify_tfm);
+ crypto_free_shash(peer_device->connection->verify_tfm);
peer_device->connection->verify_tfm = verify_tfm;
drbd_info(device, "using verify-alg: \"%s\"\n", p->verify_alg);
}
if (csums_tfm) {
strcpy(new_net_conf->csums_alg, p->csums_alg);
new_net_conf->csums_alg_len = strlen(p->csums_alg) + 1;
- crypto_free_ahash(peer_device->connection->csums_tfm);
+ crypto_free_shash(peer_device->connection->csums_tfm);
peer_device->connection->csums_tfm = csums_tfm;
drbd_info(device, "using csums-alg: \"%s\"\n", p->csums_alg);
}
@@ -3949,9 +3950,9 @@ static int receive_SyncParam(struct drbd_connection *connection, struct packet_i
mutex_unlock(&connection->resource->conf_update);
/* just for completeness: actually not needed,
* as this is not reached if csums_tfm was ok. */
- crypto_free_ahash(csums_tfm);
+ crypto_free_shash(csums_tfm);
/* but free the verify_tfm again, if csums_tfm did not work out */
- crypto_free_ahash(verify_tfm);
+ crypto_free_shash(verify_tfm);
conn_request_state(peer_device->connection, NS(conn, C_DISCONNECTING), CS_HARD);
return -EIO;
}
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 5e793dd7adfb..0b41fb0181a6 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -295,60 +295,61 @@ void drbd_request_endio(struct bio *bio)
complete_master_bio(device, &m);
}

-void drbd_csum_ee(struct crypto_ahash *tfm, struct drbd_peer_request *peer_req, void *digest)
+void drbd_csum_ee(struct crypto_shash *tfm, struct drbd_peer_request *peer_req, void *digest)
{
- AHASH_REQUEST_ON_STACK(req, tfm);
- struct scatterlist sg;
+ SHASH_DESC_ON_STACK(desc, tfm);
struct page *page = peer_req->pages;
struct page *tmp;
unsigned len;
+ void *src;

- ahash_request_set_tfm(req, tfm);
- ahash_request_set_callback(req, 0, NULL, NULL);
+ desc->tfm = tfm;
+ desc->flags = 0;

- sg_init_table(&sg, 1);
- crypto_ahash_init(req);
+ crypto_shash_init(desc);

+ src = kmap_atomic(page);
while ((tmp = page_chain_next(page))) {
/* all but the last page will be fully used */
- sg_set_page(&sg, page, PAGE_SIZE, 0);
- ahash_request_set_crypt(req, &sg, NULL, sg.length);
- crypto_ahash_update(req);
+ crypto_shash_update(desc, src, PAGE_SIZE);
+ kunmap_atomic(src);
page = tmp;
+ src = kmap_atomic(page);
}
/* and now the last, possibly only partially used page */
len = peer_req->i.size & (PAGE_SIZE - 1);
- sg_set_page(&sg, page, len ?: PAGE_SIZE, 0);
- ahash_request_set_crypt(req, &sg, digest, sg.length);
- crypto_ahash_finup(req);
- ahash_request_zero(req);
+ crypto_shash_update(desc, src, len ?: PAGE_SIZE);
+ kunmap_atomic(src);
+
+ crypto_shash_final(desc, digest);
+ shash_desc_zero(desc);
}

-void drbd_csum_bio(struct crypto_ahash *tfm, struct bio *bio, void *digest)
+void drbd_csum_bio(struct crypto_shash *tfm, struct bio *bio, void *digest)
{
- AHASH_REQUEST_ON_STACK(req, tfm);
- struct scatterlist sg;
+ SHASH_DESC_ON_STACK(desc, tfm);
struct bio_vec bvec;
struct bvec_iter iter;

- ahash_request_set_tfm(req, tfm);
- ahash_request_set_callback(req, 0, NULL, NULL);
+ desc->tfm = tfm;
+ desc->flags = 0;

- sg_init_table(&sg, 1);
- crypto_ahash_init(req);
+ crypto_shash_init(desc);

bio_for_each_segment(bvec, bio, iter) {
- sg_set_page(&sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
- ahash_request_set_crypt(req, &sg, NULL, sg.length);
- crypto_ahash_update(req);
+ u8 *src;
+
+ src = kmap_atomic(bvec.bv_page);
+ crypto_shash_update(desc, src + bvec.bv_offset, bvec.bv_len);
+ kunmap_atomic(src);
+
/* REQ_OP_WRITE_SAME has only one segment,
* checksum the payload only once. */
if (bio_op(bio) == REQ_OP_WRITE_SAME)
break;
}
- ahash_request_set_crypt(req, NULL, digest, 0);
- crypto_ahash_final(req);
- ahash_request_zero(req);
+ crypto_shash_final(desc, digest);
+ shash_desc_zero(desc);
}

/* MAYBE merge common code with w_e_end_ov_req */
@@ -367,7 +368,7 @@ static int w_e_send_csum(struct drbd_work *w, int cancel)
if (unlikely((peer_req->flags & EE_WAS_ERROR) != 0))
goto out;

- digest_size = crypto_ahash_digestsize(peer_device->connection->csums_tfm);
+ digest_size = crypto_shash_digestsize(peer_device->connection->csums_tfm);
digest = kmalloc(digest_size, GFP_NOIO);
if (digest) {
sector_t sector = peer_req->i.sector;
@@ -1205,7 +1206,7 @@ int w_e_end_csum_rs_req(struct drbd_work *w, int cancel)
* a real fix would be much more involved,
* introducing more locking mechanisms */
if (peer_device->connection->csums_tfm) {
- digest_size = crypto_ahash_digestsize(peer_device->connection->csums_tfm);
+ digest_size = crypto_shash_digestsize(peer_device->connection->csums_tfm);
D_ASSERT(device, digest_size == di->digest_size);
digest = kmalloc(digest_size, GFP_NOIO);
}
@@ -1255,7 +1256,7 @@ int w_e_end_ov_req(struct drbd_work *w, int cancel)
if (unlikely(cancel))
goto out;

- digest_size = crypto_ahash_digestsize(peer_device->connection->verify_tfm);
+ digest_size = crypto_shash_digestsize(peer_device->connection->verify_tfm);
digest = kmalloc(digest_size, GFP_NOIO);
if (!digest) {
err = 1; /* terminate the connection in case the allocation failed */
@@ -1327,7 +1328,7 @@ int w_e_end_ov_reply(struct drbd_work *w, int cancel)
di = peer_req->digest;

if (likely((peer_req->flags & EE_WAS_ERROR) == 0)) {
- digest_size = crypto_ahash_digestsize(peer_device->connection->verify_tfm);
+ digest_size = crypto_shash_digestsize(peer_device->connection->verify_tfm);
digest = kmalloc(digest_size, GFP_NOIO);
if (digest) {
drbd_csum_ee(peer_device->connection->verify_tfm, peer_req, digest);
--
2.17.1

--
Kees Cook
Pixel Security

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