# \[PATCH 4.9 150/207\] nfc: pn533: Fix double free when pn533\_fill\_fragment\_skbs() fails

- From: Greg Kroah-Hartman \<gregkh@linuxfoundation.org\>
- Date: 2021-11-24 12:22:55 
- List: stable
- Page: https://ratatoskr.run/stable/2021/11/1584059
- Thread: https://ratatoskr.run/stable/2021/11/1583929/t/2.md

```text
From: Chengfeng Ye <redacted>

[ Upstream commit 9fec40f850658e00a14a7dd9e06f7fbc7e59cc4a ]

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.

Fixes: 963a82e07d4e ("NFC: pn533: Split large Tx frames in chunks")
Fixes: 93ad42020c2d ("NFC: pn533: Target mode Tx fragmentation support")
Signed-off-by: Chengfeng Ye <redacted>
Reviewed-by: Dan Carpenter <redacted>
Reviewed-by: Krzysztof Kozlowski <redacted>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 6c495664d2cb7..806309ee41657 100644
--- a/drivers/nfc/pn533/pn533.c
+++ b/drivers/nfc/pn533/pn533.c
@@ -2075,7 +2075,7 @@ 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) {
@@ -2145,7 +2145,7 @@ 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);
@@ -2217,7 +2217,7 @@ 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 */
-- 
2.33.0



```