[permalink] [raw]

Subject: [PATCH v6 14/18] staging: rtl8192u: ieee80211: Convert from ahash to shash

This is an identical change to the wireless/lib80211 of the same name.
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.

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

Signed-off-by: Kees Cook <[email protected]>
---
.../rtl8192u/ieee80211/ieee80211_crypt_tkip.c | 57 +++++++++----------
1 file changed, 28 insertions(+), 29 deletions(-)

diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
index a7efaae4e25a..1088fa0aee0e 100644
--- a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
+++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
@@ -54,9 +54,9 @@ struct ieee80211_tkip_data {
int key_idx;

struct crypto_skcipher *rx_tfm_arc4;
- struct crypto_ahash *rx_tfm_michael;
+ struct crypto_shash *rx_tfm_michael;
struct crypto_skcipher *tx_tfm_arc4;
- struct crypto_ahash *tx_tfm_michael;
+ struct crypto_shash *tx_tfm_michael;

/* scratch buffers for virt_to_page() (crypto API) */
u8 rx_hdr[16], tx_hdr[16];
@@ -80,8 +80,7 @@ static void *ieee80211_tkip_init(int key_idx)
goto fail;
}

- priv->tx_tfm_michael = crypto_alloc_ahash("michael_mic", 0,
- CRYPTO_ALG_ASYNC);
+ priv->tx_tfm_michael = crypto_alloc_shash("michael_mic", 0, 0);
if (IS_ERR(priv->tx_tfm_michael)) {
printk(KERN_DEBUG "ieee80211_crypt_tkip: could not allocate "
"crypto API michael_mic\n");
@@ -98,8 +97,7 @@ static void *ieee80211_tkip_init(int key_idx)
goto fail;
}

- priv->rx_tfm_michael = crypto_alloc_ahash("michael_mic", 0,
- CRYPTO_ALG_ASYNC);
+ priv->rx_tfm_michael = crypto_alloc_shash("michael_mic", 0, 0);
if (IS_ERR(priv->rx_tfm_michael)) {
printk(KERN_DEBUG "ieee80211_crypt_tkip: could not allocate "
"crypto API michael_mic\n");
@@ -111,9 +109,9 @@ static void *ieee80211_tkip_init(int key_idx)

fail:
if (priv) {
- crypto_free_ahash(priv->tx_tfm_michael);
+ crypto_free_shash(priv->tx_tfm_michael);
crypto_free_skcipher(priv->tx_tfm_arc4);
- crypto_free_ahash(priv->rx_tfm_michael);
+ crypto_free_shash(priv->rx_tfm_michael);
crypto_free_skcipher(priv->rx_tfm_arc4);
kfree(priv);
}
@@ -127,9 +125,9 @@ static void ieee80211_tkip_deinit(void *priv)
struct ieee80211_tkip_data *_priv = priv;

if (_priv) {
- crypto_free_ahash(_priv->tx_tfm_michael);
+ crypto_free_shash(_priv->tx_tfm_michael);
crypto_free_skcipher(_priv->tx_tfm_arc4);
- crypto_free_ahash(_priv->rx_tfm_michael);
+ crypto_free_shash(_priv->rx_tfm_michael);
crypto_free_skcipher(_priv->rx_tfm_arc4);
}
kfree(priv);
@@ -500,30 +498,31 @@ static int ieee80211_tkip_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
return keyidx;
}

-static int michael_mic(struct crypto_ahash *tfm_michael, u8 *key, u8 *hdr,
+static int michael_mic(struct crypto_shash *tfm_michael, u8 *key, u8 *hdr,
u8 *data, size_t data_len, u8 *mic)
{
- AHASH_REQUEST_ON_STACK(req, tfm_michael);
- struct scatterlist sg[2];
+ SHASH_DESC_ON_STACK(desc, tfm_michael);
int err;

- if (tfm_michael == NULL) {
- printk(KERN_WARNING "michael_mic: tfm_michael == NULL\n");
- return -1;
- }
-
- sg_init_table(sg, 2);
- sg_set_buf(&sg[0], hdr, 16);
- sg_set_buf(&sg[1], data, data_len);
+ desc->tfm = tfm_michael;
+ desc->flags = 0;

- if (crypto_ahash_setkey(tfm_michael, key, 8))
+ if (crypto_shash_setkey(tfm_michael, key, 8))
return -1;

- ahash_request_set_tfm(req, tfm_michael);
- ahash_request_set_callback(req, 0, NULL, NULL);
- ahash_request_set_crypt(req, sg, mic, data_len + 16);
- err = crypto_ahash_digest(req);
- ahash_request_zero(req);
+ err = crypto_shash_init(desc);
+ if (err)
+ goto out;
+ err = crypto_shash_update(desc, hdr, 16);
+ if (err)
+ goto out;
+ err = crypto_shash_update(desc, data, data_len);
+ if (err)
+ goto out;
+ err = crypto_shash_final(desc, mic);
+
+out:
+ shash_desc_zero(desc);
return err;
}

@@ -663,9 +662,9 @@ static int ieee80211_tkip_set_key(void *key, int len, u8 *seq, void *priv)
{
struct ieee80211_tkip_data *tkey = priv;
int keyidx;
- struct crypto_ahash *tfm = tkey->tx_tfm_michael;
+ struct crypto_shash *tfm = tkey->tx_tfm_michael;
struct crypto_skcipher *tfm2 = tkey->tx_tfm_arc4;
- struct crypto_ahash *tfm3 = tkey->rx_tfm_michael;
+ struct crypto_shash *tfm3 = tkey->rx_tfm_michael;
struct crypto_skcipher *tfm4 = tkey->rx_tfm_arc4;

keyidx = tkey->key_idx;
--
2.17.1

2018-07-24 16:53:18

by Kees Cook

[permalink] [raw]

Subject: [PATCH v6 07/18] crypto: shash: Remove VLA usage in unaligned hashing

In the quest to remove all stack VLA usage from the kernel[1], this uses
the newly defined max alignment to perform unaligned hashing to avoid
VLAs, and drops the helper function while adding sanity checks on the
resulting buffer sizes. Additionally, the __aligned_largest macro is
removed since this helper was the only user.

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

Signed-off-by: Kees Cook <[email protected]>
---
crypto/shash.c | 27 ++++++++++++++++-----------
include/linux/compiler-gcc.h | 1 -
2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/crypto/shash.c b/crypto/shash.c
index 86d76b5c626c..d21f04d70dce 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -73,13 +73,6 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
}
EXPORT_SYMBOL_GPL(crypto_shash_setkey);

-static inline unsigned int shash_align_buffer_size(unsigned len,
- unsigned long mask)
-{
- typedef u8 __aligned_largest u8_aligned;
- return len + (mask & ~(__alignof__(u8_aligned) - 1));
-}
-
static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
unsigned int len)
{
@@ -88,11 +81,17 @@ static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
unsigned long alignmask = crypto_shash_alignmask(tfm);
unsigned int unaligned_len = alignmask + 1 -
((unsigned long)data & alignmask);
- u8 ubuf[shash_align_buffer_size(unaligned_len, alignmask)]
- __aligned_largest;
+ /*
+ * We cannot count on __aligned() working for large values:
+ * https://patchwork.kernel.org/patch/9507697/
+ */
+ u8 ubuf[MAX_ALGAPI_ALIGNMASK * 2];
u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
int err;

+ if (WARN_ON(buf + unaligned_len > ubuf + sizeof(ubuf)))
+ return -EINVAL;
+
if (unaligned_len > len)
unaligned_len = len;

@@ -124,11 +123,17 @@ static int shash_final_unaligned(struct shash_desc *desc, u8 *out)
unsigned long alignmask = crypto_shash_alignmask(tfm);
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned int ds = crypto_shash_digestsize(tfm);
- u8 ubuf[shash_align_buffer_size(ds, alignmask)]
- __aligned_largest;
+ /*
+ * We cannot count on __aligned() working for large values:
+ * https://patchwork.kernel.org/patch/9507697/
+ */
+ u8 ubuf[MAX_ALGAPI_ALIGNMASK + HASH_MAX_DIGESTSIZE];
u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
int err;

+ if (WARN_ON(buf + ds > ubuf + sizeof(ubuf)))
+ return -EINVAL;
+
err = shash->final(desc, buf);
if (err)
goto out;
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index f1a7492a5cc8..1f1cdef36a82 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -125,7 +125,6 @@
*/
#define __pure __attribute__((pure))
#define __aligned(x) __attribute__((aligned(x)))
-#define __aligned_largest __attribute__((aligned))
#define __printf(a, b) __attribute__((format(printf, a, b)))
#define __scanf(a, b) __attribute__((format(scanf, a, b)))
#define __attribute_const__ __attribute__((__const__))
--
2.17.1

2018-07-24 16:53:32

by Kees Cook

[permalink] [raw]

On Wednesday, July 25, 2018 8:01:47 PM CEST Kees Cook wrote:
> On Wed, Jul 25, 2018 at 4:32 AM, Rafael J. Wysocki <[email protected]> wrote:
> > On Tue, Jul 24, 2018 at 6:49 PM, Kees Cook <[email protected]> wrote:
> >> In the quest to remove all stack VLA usage from the kernel[1], this
> >> removes the discouraged use of AHASH_REQUEST_ON_STACK by switching to
> >> shash directly and allocating the descriptor in heap memory (which should
> >> be fine: the tfm has already been allocated there too).
> >>
> >> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
> >>
> >> Signed-off-by: Kees Cook <[email protected]>
> >> Acked-by: Pavel Machek <[email protected]>
> >
> > I think I can queue this up if there are no objections from others.
> >
> > Do you want me to do that?
>
> Sure thing. It looks like the other stand-alone patches like this one
> are getting taken into the non-crypto trees, so that's fine.
>

Applied now, thanks!