tls: rx: wrap decrypt params in a struct

The max size of iv + aad + tail is 22B. That's smaller
than a single sg entry (32B). Don't bother with the
memory packing, just create a struct which holds the
max size of those members.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/tls/tls_sw.c

@@ -50,6 +50,13 @@ struct tls_decrypt_arg {
 	u8 tail;
 };
 
+struct tls_decrypt_ctx {
+	u8 iv[MAX_IV_SIZE];
+	u8 aad[TLS_MAX_AAD_SIZE];
+	u8 tail;
+	struct scatterlist sg[];
+};
+
 noinline void tls_err_abort(struct sock *sk, int err)
 {
 	WARN_ON_ONCE(err >= 0);
@@ -1414,17 +1421,18 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_sw_context_rx *ctx = tls_sw_ctx_rx(tls_ctx);
 	struct tls_prot_info *prot = &tls_ctx->prot_info;
+	int n_sgin, n_sgout, aead_size, err, pages = 0;
 	struct strp_msg *rxm = strp_msg(skb);
 	struct tls_msg *tlm = tls_msg(skb);
-	int n_sgin, n_sgout, nsg, mem_size, aead_size, err, pages = 0;
-	u8 *aad, *iv, *tail, *mem = NULL;
 	struct aead_request *aead_req;
 	struct sk_buff *unused;
 	struct scatterlist *sgin = NULL;
 	struct scatterlist *sgout = NULL;
 	const int data_len = rxm->full_len - prot->overhead_size;
 	int tail_pages = !!prot->tail_size;
+	struct tls_decrypt_ctx *dctx;
 	int iv_offset = 0;
+	u8 *mem;
 
 	if (darg->zc && (out_iov || out_sg)) {
 		if (out_iov)
@@ -1446,38 +1454,30 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 	/* Increment to accommodate AAD */
 	n_sgin = n_sgin + 1;
 
-	nsg = n_sgin + n_sgout;
-
-	aead_size = sizeof(*aead_req) + crypto_aead_reqsize(ctx->aead_recv);
-	mem_size = aead_size + (nsg * sizeof(struct scatterlist));
-	mem_size = mem_size + TLS_MAX_AAD_SIZE;
-	mem_size = mem_size + MAX_IV_SIZE;
-	mem_size = mem_size + prot->tail_size;
-
 	/* Allocate a single block of memory which contains
-	 * aead_req || sgin[] || sgout[] || aad || iv || tail.
-	 * This order achieves correct alignment for aead_req, sgin, sgout.
+	 *   aead_req || tls_decrypt_ctx.
+	 * Both structs are variable length.
 	 */
-	mem = kmalloc(mem_size, sk->sk_allocation);
+	aead_size = sizeof(*aead_req) + crypto_aead_reqsize(ctx->aead_recv);
+	mem = kmalloc(aead_size + struct_size(dctx, sg, n_sgin + n_sgout),
+		      sk->sk_allocation);
 	if (!mem)
 		return -ENOMEM;
 
 	/* Segment the allocated memory */
 	aead_req = (struct aead_request *)mem;
-	sgin = (struct scatterlist *)(mem + aead_size);
-	sgout = sgin + n_sgin;
-	aad = (u8 *)(sgout + n_sgout);
-	iv = aad + TLS_MAX_AAD_SIZE;
-	tail = iv + MAX_IV_SIZE;
+	dctx = (struct tls_decrypt_ctx *)(mem + aead_size);
+	sgin = &dctx->sg[0];
+	sgout = &dctx->sg[n_sgin];
 
 	/* For CCM based ciphers, first byte of nonce+iv is a constant */
 	switch (prot->cipher_type) {
 	case TLS_CIPHER_AES_CCM_128:
-		iv[0] = TLS_AES_CCM_IV_B0_BYTE;
+		dctx->iv[0] = TLS_AES_CCM_IV_B0_BYTE;
 		iv_offset = 1;
 		break;
 	case TLS_CIPHER_SM4_CCM:
-		iv[0] = TLS_SM4_CCM_IV_B0_BYTE;
+		dctx->iv[0] = TLS_SM4_CCM_IV_B0_BYTE;
 		iv_offset = 1;
 		break;
 	}
@@ -1485,28 +1485,28 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 	/* Prepare IV */
 	if (prot->version == TLS_1_3_VERSION ||
 	    prot->cipher_type == TLS_CIPHER_CHACHA20_POLY1305) {
-		memcpy(iv + iv_offset, tls_ctx->rx.iv,
+		memcpy(&dctx->iv[iv_offset], tls_ctx->rx.iv,
 		       prot->iv_size + prot->salt_size);
 	} else {
 		err = skb_copy_bits(skb, rxm->offset + TLS_HEADER_SIZE,
-				    iv + iv_offset + prot->salt_size,
+				    &dctx->iv[iv_offset] + prot->salt_size,
 				    prot->iv_size);
 		if (err < 0) {
 			kfree(mem);
 			return err;
 		}
-		memcpy(iv + iv_offset, tls_ctx->rx.iv, prot->salt_size);
+		memcpy(&dctx->iv[iv_offset], tls_ctx->rx.iv, prot->salt_size);
 	}
-	xor_iv_with_seq(prot, iv + iv_offset, tls_ctx->rx.rec_seq);
+	xor_iv_with_seq(prot, &dctx->iv[iv_offset], tls_ctx->rx.rec_seq);
 
 	/* Prepare AAD */
-	tls_make_aad(aad, rxm->full_len - prot->overhead_size +
+	tls_make_aad(dctx->aad, rxm->full_len - prot->overhead_size +
 		     prot->tail_size,
 		     tls_ctx->rx.rec_seq, tlm->control, prot);
 
 	/* Prepare sgin */
 	sg_init_table(sgin, n_sgin);
-	sg_set_buf(&sgin[0], aad, prot->aad_size);
+	sg_set_buf(&sgin[0], dctx->aad, prot->aad_size);
 	err = skb_to_sgvec(skb, &sgin[1],
 			   rxm->offset + prot->prepend_size,
 			   rxm->full_len - prot->prepend_size);
@@ -1518,7 +1518,7 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 	if (n_sgout) {
 		if (out_iov) {
 			sg_init_table(sgout, n_sgout);
-			sg_set_buf(&sgout[0], aad, prot->aad_size);
+			sg_set_buf(&sgout[0], dctx->aad, prot->aad_size);
 
 			err = tls_setup_from_iter(out_iov, data_len,
 						  &pages, &sgout[1],
@@ -1528,7 +1528,7 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 
 			if (prot->tail_size) {
 				sg_unmark_end(&sgout[pages]);
-				sg_set_buf(&sgout[pages + 1], tail,
+				sg_set_buf(&sgout[pages + 1], &dctx->tail,
 					   prot->tail_size);
 				sg_mark_end(&sgout[pages + 1]);
 			}
@@ -1545,13 +1545,13 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 	}
 
 	/* Prepare and submit AEAD request */
-	err = tls_do_decryption(sk, skb, sgin, sgout, iv,
+	err = tls_do_decryption(sk, skb, sgin, sgout, dctx->iv,
 				data_len + prot->tail_size, aead_req, darg);
 	if (darg->async)
 		return 0;
 
 	if (prot->tail_size)
-		darg->tail = *tail;
+		darg->tail = dctx->tail;
 
 	/* Release the pages in case iov was mapped to pages */
 	for (; pages > 0; pages--)