usb: dwc3: gadget: Don't setup more than requested

The SG list may be set up with entry size more than the requested
length. Check the usb_request->length and make sure that we don't setup
the TRBs to send/receive more than requested. This case may occur when
the SG entry is allocated up to a certain minimum size, but the request
length is less than that. It can also occur when the request is reused
for a different request length.

Cc: <stable@vger.kernel.org> # v4.18+
Fixes: a31e63b ("usb: dwc3: gadget: Correct handling of scattergather lists")
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/dwc3/gadget.c

@@ -1054,27 +1054,25 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *dep, struct dwc3_trb *trb,
  * dwc3_prepare_one_trb - setup one TRB from one request
  * @dep: endpoint for which this request is prepared
  * @req: dwc3_request pointer
+ * @trb_length: buffer size of the TRB
  * @chain: should this TRB be chained to the next?
  * @node: only for isochronous endpoints. First TRB needs different type.
  */
 static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
-		struct dwc3_request *req, unsigned chain, unsigned node)
+		struct dwc3_request *req, unsigned int trb_length,
+		unsigned chain, unsigned node)
 {
 	struct dwc3_trb		*trb;
-	unsigned int		length;
 	dma_addr_t		dma;
 	unsigned		stream_id = req->request.stream_id;
 	unsigned		short_not_ok = req->request.short_not_ok;
 	unsigned		no_interrupt = req->request.no_interrupt;
 	unsigned		is_last = req->request.is_last;
 
-	if (req->request.num_sgs > 0) {
-		length = sg_dma_len(req->start_sg);
+	if (req->request.num_sgs > 0)
 		dma = sg_dma_address(req->start_sg);
-	} else {
-		length = req->request.length;
+	else
 		dma = req->request.dma;
-	}
 
 	trb = &dep->trb_pool[dep->trb_enqueue];
 
@@ -1086,7 +1084,7 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 
 	req->num_trbs++;
 
-	__dwc3_prepare_one_trb(dep, trb, dma, length, chain, node,
+	__dwc3_prepare_one_trb(dep, trb, dma, trb_length, chain, node,
 			stream_id, short_not_ok, no_interrupt, is_last);
 }
 
@@ -1096,24 +1094,35 @@ static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
 	struct scatterlist *sg = req->start_sg;
 	struct scatterlist *s;
 	int		i;
-
+	unsigned int length = req->request.length;
 	unsigned int remaining = req->request.num_mapped_sgs
 		- req->num_queued_sgs;
 
+	/*
+	 * If we resume preparing the request, then get the remaining length of
+	 * the request and resume where we left off.
+	 */
+	for_each_sg(req->request.sg, s, req->num_queued_sgs, i)
+		length -= sg_dma_len(s);
+
 	for_each_sg(sg, s, remaining, i) {
-		unsigned int length = req->request.length;
 		unsigned int maxp = usb_endpoint_maxp(dep->endpoint.desc);
 		unsigned int rem = length % maxp;
+		unsigned int trb_length;
 		unsigned chain = true;
 
+		trb_length = min_t(unsigned int, length, sg_dma_len(s));
+
+		length -= trb_length;
+
 		/*
 		 * IOMMU driver is coalescing the list of sgs which shares a
 		 * page boundary into one and giving it to USB driver. With
 		 * this the number of sgs mapped is not equal to the number of
 		 * sgs passed. So mark the chain bit to false if it isthe last
 		 * mapped sg.
 		 */
-		if (i == remaining - 1)
+		if ((i == remaining - 1) || !length)
 			chain = false;
 
 		if (rem && usb_endpoint_dir_out(dep->endpoint.desc) && !chain) {
@@ -1123,7 +1132,7 @@ static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
 			req->needs_extra_trb = true;
 
 			/* prepare normal TRB */
-			dwc3_prepare_one_trb(dep, req, true, i);
+			dwc3_prepare_one_trb(dep, req, trb_length, true, i);
 
 			/* Now prepare one extra TRB to align transfer size */
 			trb = &dep->trb_pool[dep->trb_enqueue];
@@ -1135,7 +1144,7 @@ static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
 					req->request.no_interrupt,
 					req->request.is_last);
 		} else {
-			dwc3_prepare_one_trb(dep, req, chain, i);
+			dwc3_prepare_one_trb(dep, req, trb_length, chain, i);
 		}
 
 		/*
@@ -1150,6 +1159,16 @@ static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
 
 		req->num_queued_sgs++;
 
+		/*
+		 * The number of pending SG entries may not correspond to the
+		 * number of mapped SG entries. If all the data are queued, then
+		 * don't include unused SG entries.
+		 */
+		if (length == 0) {
+			req->num_pending_sgs -= req->request.num_mapped_sgs - req->num_queued_sgs;
+			break;
+		}
+
 		if (!dwc3_calc_trbs_left(dep))
 			break;
 	}
@@ -1169,7 +1188,7 @@ static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
 		req->needs_extra_trb = true;
 
 		/* prepare normal TRB */
-		dwc3_prepare_one_trb(dep, req, true, 0);
+		dwc3_prepare_one_trb(dep, req, length, true, 0);
 
 		/* Now prepare one extra TRB to align transfer size */
 		trb = &dep->trb_pool[dep->trb_enqueue];
@@ -1187,7 +1206,7 @@ static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
 		req->needs_extra_trb = true;
 
 		/* prepare normal TRB */
-		dwc3_prepare_one_trb(dep, req, true, 0);
+		dwc3_prepare_one_trb(dep, req, length, true, 0);
 
 		/* Now prepare one extra TRB to handle ZLP */
 		trb = &dep->trb_pool[dep->trb_enqueue];
@@ -1198,7 +1217,7 @@ static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
 				req->request.no_interrupt,
 				req->request.is_last);
 	} else {
-		dwc3_prepare_one_trb(dep, req, false, 0);
+		dwc3_prepare_one_trb(dep, req, length, false, 0);
 	}
 }