crypto: x86/chacha20 - Manually align stack buffer

[Herbert Xu <herbert@gondor.apana.org.au>]

The kernel on x86-64 cannot use gcc attribute align to align to
a 16-byte boundary.  This patch reverts to the old way of aligning
it by hand.

Incidentally the old way was actually broken in not allocating
enough space and would silently corrupt the stack.  This patch
fixes it by allocating an extra 8 bytes.

Fixes: 9ae433bc79f9 ("crypto: chacha20 - convert generic and...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/arch/x86/crypto/chacha20_glue.c b/arch/x86/crypto/chacha20_glue.c
index 78f75b0..054306d 100644
--- a/arch/x86/crypto/chacha20_glue.c
+++ b/arch/x86/crypto/chacha20_glue.c
@@ -67,10 +67,13 @@ static int chacha20_simd(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
-	u32 state[16] __aligned(CHACHA20_STATE_ALIGN);
+	u32 *state, state_buf[16 + 8] __aligned(8);
 	struct skcipher_walk walk;
 	int err;
 
+	BUILD_BUG_ON(CHACHA20_STATE_ALIGN != 16);
+	state = PTR_ALIGN(state_buf + 0, CHACHA20_STATE_ALIGN);
+
 	if (req->cryptlen <= CHACHA20_BLOCK_SIZE || !may_use_simd())
 		return crypto_chacha20_crypt(req);
 
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt