[PATCH 4.19 203/639] mt76: usb: fix possible memory leak in mt76u_buf_free

[Greg Kroah-Hartman]

From: Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx>

[ Upstream commit cb83585e1121bd6d6c039cf09fa32380bf8b6258 ]

Move q->ndesc initialization before the for loop in mt76u_alloc_rx
since otherwise allocated urbs will not be freed in mt76u_buf_free
Double-check scatterlist pointer in mt76u_buf_free

Fixes: b40b15e1521f ("mt76: add usb support to mt76 layer")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx>
Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/wireless/mediatek/mt76/usb.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/mediatek/mt76/usb.c
index 8d40e92fb6f27..dcf927de65f39 100644
--- a/drivers/net/wireless/mediatek/mt76/usb.c
+++ b/drivers/net/wireless/mediatek/mt76/usb.c
@@ -273,10 +273,16 @@ EXPORT_SYMBOL_GPL(mt76u_buf_alloc);
 void mt76u_buf_free(struct mt76u_buf *buf)
 {
 	struct urb *urb = buf->urb;
+	struct scatterlist *sg;
 	int i;
 
-	for (i = 0; i < urb->num_sgs; i++)
-		skb_free_frag(sg_virt(&urb->sg[i]));
+	for (i = 0; i < urb->num_sgs; i++) {
+		sg = &urb->sg[i];
+		if (!sg)
+			continue;
+
+		skb_free_frag(sg_virt(sg));
+	}
 	usb_free_urb(buf->urb);
 }
 EXPORT_SYMBOL_GPL(mt76u_buf_free);
@@ -478,7 +484,8 @@ static int mt76u_alloc_rx(struct mt76_dev *dev)
 		nsgs = 1;
 	}
 
-	for (i = 0; i < MT_NUM_RX_ENTRIES; i++) {
+	q->ndesc = MT_NUM_RX_ENTRIES;
+	for (i = 0; i < q->ndesc; i++) {
 		err = mt76u_buf_alloc(dev, &q->entry[i].ubuf,
 				      nsgs, q->buf_size,
 				      SKB_WITH_OVERHEAD(q->buf_size),
@@ -486,7 +493,6 @@ static int mt76u_alloc_rx(struct mt76_dev *dev)
 		if (err < 0)
 			return err;
 	}
-	q->ndesc = MT_NUM_RX_ENTRIES;
 
 	return mt76u_submit_rx_buffers(dev);
 }
-- 
2.20.1