linux-kernel - [PATCH v2] nfc: pn533: Fix double free when pn533_fill_fragment

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Message-Id: <20211105133636.31282-1-cyeaa@connect.ust.hk>
Date:   Fri,  5 Nov 2021 06:36:36 -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 v2] 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 in error path of pn533_fill_fragment_skbs.

Signed-off-by: Chengfeng Ye <cyeaa@...nect.ust.hk>
---
 drivers/nfc/pn533/pn533.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/nfc/pn533/pn533.c b/drivers/nfc/pn533/pn533.c
index 787bcbd290f7..a491db46e3bd 100644
--- a/drivers/nfc/pn533/pn533.c
+++ b/drivers/nfc/pn533/pn533.c
@@ -2216,7 +2216,7 @@ static int pn533_fill_fragment_skbs(struct pn533 *dev, struct sk_buff *skb)
 		frag = pn533_alloc_skb(dev, frag_size);
 		if (!frag) {
 			skb_queue_purge(&dev->fragment_skb);
-			break;
+			return -ENOMEM;
 		}
 
 		if (!dev->tgt_mode) {
@@ -2285,7 +2285,7 @@ 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)
+			if (rc < 0)
 				goto error;
 
 			skb = skb_dequeue(&dev->fragment_skb);
@@ -2353,7 +2353,7 @@ 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)
+		if (rc < 0)
 			goto error;
 
 		/* get the first skb */
-- 
2.17.1