s390/crypto: fix gcm-aes-s390 selftest failures

The current kernel uses improved crypto selftests. These
tests showed that the current implementation of gcm-aes-s390
is not able to deal with chunks of output buffers which are
not a multiple of 16 bytes. This patch introduces a rework
of the gcm aes s390 scatter walk handling which now is able
to handle any input and output scatter list chunk sizes
correctly.

Code has been verified by the crypto selftests, the tcrypt
kernel module and additional tests ran via the af_alg interface.

Cc: <stable@vger.kernel.org>
Reported-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Patrick Steuer <steuer@linux.ibm.com>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

arch/s390/crypto/aes_s390.c

@@ -826,7 +826,7 @@ static int gcm_aes_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
 	return 0;
 }
 
-static void gcm_sg_walk_start(struct gcm_sg_walk *gw, struct scatterlist *sg,
+static void gcm_walk_start(struct gcm_sg_walk *gw, struct scatterlist *sg,
 			   unsigned int len)
 {
 	memset(gw, 0, sizeof(*gw));
@@ -834,11 +834,37 @@ static void gcm_sg_walk_start(struct gcm_sg_walk *gw, struct scatterlist *sg,
 	scatterwalk_start(&gw->walk, sg);
 }
 
-static int gcm_sg_walk_go(struct gcm_sg_walk *gw, unsigned int minbytesneeded)
+static inline unsigned int _gcm_sg_clamp_and_map(struct gcm_sg_walk *gw)
+{
+	struct scatterlist *nextsg;
+
+	gw->walk_bytes = scatterwalk_clamp(&gw->walk, gw->walk_bytes_remain);
+	while (!gw->walk_bytes) {
+		nextsg = sg_next(gw->walk.sg);
+		if (!nextsg)
+			return 0;
+		scatterwalk_start(&gw->walk, nextsg);
+		gw->walk_bytes = scatterwalk_clamp(&gw->walk,
+						   gw->walk_bytes_remain);
+	}
+	gw->walk_ptr = scatterwalk_map(&gw->walk);
+	return gw->walk_bytes;
+}
+
+static inline void _gcm_sg_unmap_and_advance(struct gcm_sg_walk *gw,
+					     unsigned int nbytes)
+{
+	gw->walk_bytes_remain -= nbytes;
+	scatterwalk_unmap(&gw->walk);
+	scatterwalk_advance(&gw->walk, nbytes);
+	scatterwalk_done(&gw->walk, 0, gw->walk_bytes_remain);
+	gw->walk_ptr = NULL;
+}
+
+static int gcm_in_walk_go(struct gcm_sg_walk *gw, unsigned int minbytesneeded)
 {
 	int n;
 
-	/* minbytesneeded <= AES_BLOCK_SIZE */
 	if (gw->buf_bytes && gw->buf_bytes >= minbytesneeded) {
 		gw->ptr = gw->buf;
 		gw->nbytes = gw->buf_bytes;
@@ -851,13 +877,11 @@ static int gcm_sg_walk_go(struct gcm_sg_walk *gw, unsigned int minbytesneeded)
 		goto out;
 	}
 
-	gw->walk_bytes = scatterwalk_clamp(&gw->walk, gw->walk_bytes_remain);
-	if (!gw->walk_bytes) {
-		scatterwalk_start(&gw->walk, sg_next(gw->walk.sg));
-		gw->walk_bytes = scatterwalk_clamp(&gw->walk,
-						   gw->walk_bytes_remain);
+	if (!_gcm_sg_clamp_and_map(gw)) {
+		gw->ptr = NULL;
+		gw->nbytes = 0;
+		goto out;
 	}
-	gw->walk_ptr = scatterwalk_map(&gw->walk);
 
 	if (!gw->buf_bytes && gw->walk_bytes >= minbytesneeded) {
 		gw->ptr = gw->walk_ptr;
@@ -869,51 +893,90 @@ static int gcm_sg_walk_go(struct gcm_sg_walk *gw, unsigned int minbytesneeded)
 		n = min(gw->walk_bytes, AES_BLOCK_SIZE - gw->buf_bytes);
 		memcpy(gw->buf + gw->buf_bytes, gw->walk_ptr, n);
 		gw->buf_bytes += n;
-		gw->walk_bytes_remain -= n;
-		scatterwalk_unmap(&gw->walk);
-		scatterwalk_advance(&gw->walk, n);
-		scatterwalk_done(&gw->walk, 0, gw->walk_bytes_remain);
-
+		_gcm_sg_unmap_and_advance(gw, n);
 		if (gw->buf_bytes >= minbytesneeded) {
 			gw->ptr = gw->buf;
 			gw->nbytes = gw->buf_bytes;
 			goto out;
 		}
-
-		gw->walk_bytes = scatterwalk_clamp(&gw->walk,
-						   gw->walk_bytes_remain);
-		if (!gw->walk_bytes) {
-			scatterwalk_start(&gw->walk, sg_next(gw->walk.sg));
-			gw->walk_bytes = scatterwalk_clamp(&gw->walk,
-							gw->walk_bytes_remain);
+		if (!_gcm_sg_clamp_and_map(gw)) {
+			gw->ptr = NULL;
+			gw->nbytes = 0;
+			goto out;
 		}
-		gw->walk_ptr = scatterwalk_map(&gw->walk);
 	}
 
 out:
 	return gw->nbytes;
 }
 
-static void gcm_sg_walk_done(struct gcm_sg_walk *gw, unsigned int bytesdone)
+static int gcm_out_walk_go(struct gcm_sg_walk *gw, unsigned int minbytesneeded)
 {
-	int n;
+	if (gw->walk_bytes_remain == 0) {
+		gw->ptr = NULL;
+		gw->nbytes = 0;
+		goto out;
+	}
+
+	if (!_gcm_sg_clamp_and_map(gw)) {
+		gw->ptr = NULL;
+		gw->nbytes = 0;
+		goto out;
+	}
+
+	if (gw->walk_bytes >= minbytesneeded) {
+		gw->ptr = gw->walk_ptr;
+		gw->nbytes = gw->walk_bytes;
+		goto out;
+	}
+
+	scatterwalk_unmap(&gw->walk);
+	gw->walk_ptr = NULL;
+
+	gw->ptr = gw->buf;
+	gw->nbytes = sizeof(gw->buf);
+
+out:
+	return gw->nbytes;
+}
 
+static int gcm_in_walk_done(struct gcm_sg_walk *gw, unsigned int bytesdone)
+{
 	if (gw->ptr == NULL)
-		return;
+		return 0;
 
 	if (gw->ptr == gw->buf) {
-		n = gw->buf_bytes - bytesdone;
+		int n = gw->buf_bytes - bytesdone;
 		if (n > 0) {
 			memmove(gw->buf, gw->buf + bytesdone, n);
-			gw->buf_bytes -= n;
+			gw->buf_bytes = n;
 		} else
 			gw->buf_bytes = 0;
-	} else {
-		gw->walk_bytes_remain -= bytesdone;
-		scatterwalk_unmap(&gw->walk);
-		scatterwalk_advance(&gw->walk, bytesdone);
-		scatterwalk_done(&gw->walk, 0, gw->walk_bytes_remain);
+	} else
+		_gcm_sg_unmap_and_advance(gw, bytesdone);
+
+	return bytesdone;
+}
+
+static int gcm_out_walk_done(struct gcm_sg_walk *gw, unsigned int bytesdone)
+{
+	int i, n;
+
+	if (gw->ptr == NULL)
+		return 0;
+
+	if (gw->ptr == gw->buf) {
+		for (i = 0; i < bytesdone; i += n) {
+			if (!_gcm_sg_clamp_and_map(gw))
+				return i;
+			n = min(gw->walk_bytes, bytesdone - i);
+			memcpy(gw->walk_ptr, gw->buf + i, n);
+			_gcm_sg_unmap_and_advance(gw, n);
 		}
+	} else
+		_gcm_sg_unmap_and_advance(gw, bytesdone);
+
+	return bytesdone;
 }
 
 static int gcm_aes_crypt(struct aead_request *req, unsigned int flags)
@@ -926,7 +989,7 @@ static int gcm_aes_crypt(struct aead_request *req, unsigned int flags)
 	unsigned int pclen = req->cryptlen;
 	int ret = 0;
 
-	unsigned int len, in_bytes, out_bytes,
+	unsigned int n, len, in_bytes, out_bytes,
 		     min_bytes, bytes, aad_bytes, pc_bytes;
 	struct gcm_sg_walk gw_in, gw_out;
 	u8 tag[GHASH_DIGEST_SIZE];
@@ -963,14 +1026,14 @@ static int gcm_aes_crypt(struct aead_request *req, unsigned int flags)
 	*(u32 *)(param.j0 + ivsize) = 1;
 	memcpy(param.k, ctx->key, ctx->key_len);
 
-	gcm_sg_walk_start(&gw_in, req->src, len);
-	gcm_sg_walk_start(&gw_out, req->dst, len);
+	gcm_walk_start(&gw_in, req->src, len);
+	gcm_walk_start(&gw_out, req->dst, len);
 
 	do {
 		min_bytes = min_t(unsigned int,
 				  aadlen > 0 ? aadlen : pclen, AES_BLOCK_SIZE);
-		in_bytes = gcm_sg_walk_go(&gw_in, min_bytes);
-		out_bytes = gcm_sg_walk_go(&gw_out, min_bytes);
+		in_bytes = gcm_in_walk_go(&gw_in, min_bytes);
+		out_bytes = gcm_out_walk_go(&gw_out, min_bytes);
 		bytes = min(in_bytes, out_bytes);
 
 		if (aadlen + pclen <= bytes) {
@@ -997,8 +1060,11 @@ static int gcm_aes_crypt(struct aead_request *req, unsigned int flags)
 			  gw_in.ptr + aad_bytes, pc_bytes,
 			  gw_in.ptr, aad_bytes);
 
-		gcm_sg_walk_done(&gw_in, aad_bytes + pc_bytes);
-		gcm_sg_walk_done(&gw_out, aad_bytes + pc_bytes);
+		n = aad_bytes + pc_bytes;
+		if (gcm_in_walk_done(&gw_in, n) != n)
+			return -ENOMEM;
+		if (gcm_out_walk_done(&gw_out, n) != n)
+			return -ENOMEM;
 		aadlen -= aad_bytes;
 		pclen -= pc_bytes;
 	} while (aadlen + pclen > 0);