[PATCH 4/5] KEYS: DH: ensure the KDF counter is properly aligned

[Eric Biggers]

From: Eric Biggers <ebigg...@google.com>

Accessing a 'u8[4]' through a '__be32 *' violates alignment rules.  Just
make the counter a __be32 instead.

Signed-off-by: Eric Biggers <ebigg...@google.com>
---
 security/keys/dh.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/security/keys/dh.c b/security/keys/dh.c
index a3a8607107f5..e6b757c33289 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -130,14 +130,6 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc)
        kzfree(sdesc);
 }
 
-/* convert 32 bit integer into its string representation */
-static inline void crypto_kw_cpu_to_be32(u32 val, u8 *buf)
-{
-       __be32 *a = (__be32 *)buf;
-
-       *a = cpu_to_be32(val);
-}
-
 /*
  * Implementation of the KDF in counter mode according to SP800-108 section 5.1
  * as well as SP800-56A section 5.8.1 (Single-step KDF).
@@ -154,16 +146,14 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 
*src, unsigned int slen,
        unsigned int h = crypto_shash_digestsize(desc->tfm);
        int err = 0;
        u8 *dst_orig = dst;
-       u32 i = 1;
-       u8 iteration[sizeof(u32)];
+       __be32 counter = cpu_to_be32(1);
 
        while (dlen) {
                err = crypto_shash_init(desc);
                if (err)
                        goto err;
 
-               crypto_kw_cpu_to_be32(i, iteration);
-               err = crypto_shash_update(desc, iteration, sizeof(u32));
+               err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32));
                if (err)
                        goto err;
 
@@ -189,7 +179,7 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, 
unsigned int slen,
 
                        dlen -= h;
                        dst += h;
-                       i++;
+                       counter = cpu_to_be32(be32_to_cpu(counter) + 1);
                }
        }
 
-- 
2.12.2