linux-kernel - [PATCH v2] rtl818x_pci: Fix potential memory leaks in rtl8180_init_rx

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Message-ID: <20251114094527.79842-1-nihaal@cse.iitm.ac.in>
Date: Fri, 14 Nov 2025 15:15:26 +0530
From: Abdun Nihaal <nihaal@....iitm.ac.in>
To: Ping-Ke Shih <pkshih@...ltek.com>,
	linux-wireless@...r.kernel.org
Cc: Abdun Nihaal <nihaal@....iitm.ac.in>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] rtl818x_pci: Fix potential memory leaks in rtl8180_init_rx_ring()

In rtl8180_init_rx_ring(), memory is allocated for skb packets and DMA
allocations in a loop. When an allocation fails, the previously
successful allocations are not freed on exit.

Fix that by jumping to err_free_rings label on error, which calls
rtl8180_free_rx_ring() to free the allocations. Remove the free of
rx_ring in rtl8180_init_rx_ring() error path, and set the freed
priv->rx_buf entry to null, to avoid double free.

Fixes: f653211197f3 ("Add rtl8180 wireless driver")
Signed-off-by: Abdun Nihaal <nihaal@....iitm.ac.in>
---

v1->v2:
- Use rtl8180_free_rx_ring() to free the buffers by jumping to
  err_free_rings label, as suggested by Ping-Ke Shih.
- Remove free of rx_ring and set the freed priv->rx_buf entry to null,
  in the error path to avoid it getting freed again in 
  rtl8180_free_rx_ring()

Calling rtl8180_free_rx_ring() directly in rtl8180_init_rx_ring()
requires moving the free function before (implicit declaration error).
So in order to minimize the code change, I used the err_free_rings label
as suggested by Ping-Ke Shih.

Link to v1:
https://lore.kernel.org/all/20251113165851.39054-1-nihaal@cse.iitm.ac.in/

 drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c b/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c
index 2905baea6239..070c0431c482 100644
--- a/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c
+++ b/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c
@@ -1023,9 +1023,6 @@ static int rtl8180_init_rx_ring(struct ieee80211_hw *dev)
 		dma_addr_t *mapping;
 		entry = priv->rx_ring + priv->rx_ring_sz*i;
 		if (!skb) {
-			dma_free_coherent(&priv->pdev->dev,
-					  priv->rx_ring_sz * 32,
-					  priv->rx_ring, priv->rx_ring_dma);
 			wiphy_err(dev->wiphy, "Cannot allocate RX skb\n");
 			return -ENOMEM;
 		}
@@ -1037,9 +1034,7 @@ static int rtl8180_init_rx_ring(struct ieee80211_hw *dev)
 
 		if (dma_mapping_error(&priv->pdev->dev, *mapping)) {
 			kfree_skb(skb);
-			dma_free_coherent(&priv->pdev->dev,
-					  priv->rx_ring_sz * 32,
-					  priv->rx_ring, priv->rx_ring_dma);
+			priv->rx_buf[i] = NULL;
 			wiphy_err(dev->wiphy, "Cannot map DMA for RX skb\n");
 			return -ENOMEM;
 		}
@@ -1130,7 +1125,7 @@ static int rtl8180_start(struct ieee80211_hw *dev)
 
 	ret = rtl8180_init_rx_ring(dev);
 	if (ret)
-		return ret;
+		goto err_free_rings;
 
 	for (i = 0; i < (dev->queues + 1); i++)
 		if ((ret = rtl8180_init_tx_ring(dev, i, 16)))
-- 
2.43.0