crypto: simd - correctly take reqsize of wrapped skcipher into account

The simd wrapper's skcipher request context structure consists
of a single subrequest whose size is taken from the subordinate
skcipher. However, in simd_skcipher_init(), the reqsize that is
retrieved is not from the subordinate skcipher but from the
cryptd request structure, whose size is completely unrelated to
the actual wrapped skcipher.
Reported-by: Qian Cai <cai@gmx.us>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Qian Cai <cai@gmx.us>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/simd.c

@@ -124,8 +124,9 @@ static int simd_skcipher_init(struct crypto_skcipher *tfm)
 
 	ctx->cryptd_tfm = cryptd_tfm;
 
-	reqsize = sizeof(struct skcipher_request);
-	reqsize += crypto_skcipher_reqsize(&cryptd_tfm->base);
+	reqsize = crypto_skcipher_reqsize(cryptd_skcipher_child(cryptd_tfm));
+	reqsize = max(reqsize, crypto_skcipher_reqsize(&cryptd_tfm->base));
+	reqsize += sizeof(struct skcipher_request);
 
 	crypto_skcipher_set_reqsize(tfm, reqsize);