linux-kernel - [PATCH] nfc: pn533: Fix double free when pn533_fill_fragment

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Date:   Fri,  5 Nov 2021 06:18:51 -0700
From:   Chengfeng Ye <cyeaa@...nect.ust.hk>
To:     krzysztof.kozlowski@...onical.com, davem@...emloft.net,
        kuba@...nel.org, wengjianfeng@...ong.com, dan.carpenter@...cle.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chengfeng Ye <cyeaa@...nect.ust.hk>
Subject: [PATCH] nfc: pn533: Fix double free when pn533_fill_fragment_skbs() fails

skb is already freed by dev_kfree_skb in pn533_fill_fragment_skbs,
but follow error handler branch when pn533_fill_fragment_skbs()
fails, skb is freed again, results in double free issue. Fix this
by not free skb when pn533_fill_fragment_skbs() return value <= 0.

Signed-off-by: Chengfeng Ye <cyeaa@...nect.ust.hk>
---
 drivers/nfc/pn533/pn533.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/nfc/pn533/pn533.c b/drivers/nfc/pn533/pn533.c
index 787bcbd290f7..226ae4357f7f 100644
--- a/drivers/nfc/pn533/pn533.c
+++ b/drivers/nfc/pn533/pn533.c
@@ -2285,8 +2285,10 @@ static int pn533_transceive(struct nfc_dev *nfc_dev,
 		/* jumbo frame ? */
 		if (skb->len > PN533_CMD_DATAEXCH_DATA_MAXLEN) {
 			rc = pn533_fill_fragment_skbs(dev, skb);
-			if (rc <= 0)
-				goto error;
+			if (rc <= 0) {
+				kfree(arg);
+				return rc;
+			}
 
 			skb = skb_dequeue(&dev->fragment_skb);
 			if (!skb) {
@@ -2353,8 +2355,11 @@ static int pn533_tm_send(struct nfc_dev *nfc_dev, struct sk_buff *skb)
 	/* let's split in multiple chunks if size's too big */
 	if (skb->len > PN533_CMD_DATAEXCH_DATA_MAXLEN) {
 		rc = pn533_fill_fragment_skbs(dev, skb);
-		if (rc <= 0)
-			goto error;
+		if (rc <= 0) {
+			if (rc < 0)
+				skb_queue_purge(&dev->fragment_skb);
+			return rc;
+		}
 
 		/* get the first skb */
 		skb = skb_dequeue(&dev->fragment_skb);
-- 
2.17.1