[PATCH net 1/5] nfc: nci: free skb on nci_transceive early error paths

[Jakub Kicinski <kuba@kernel.org>]

nci_transceive() takes ownership of the skb passed by the caller,
but the -EPROTO, -EINVAL, and -EBUSY error paths return without
freeing it.

Due to issues clearing NCI_DATA_EXCHANGE fixed by subsequent changes
the nci/nci_dev selftest hits the error path occasionally in NIPA,
and kmemleak detects leaks:

unreferenced object 0xff11000015ce6a40 (size 640):
  comm "nci_dev", pid 3954, jiffies 4295441246
  hex dump (first 32 bytes):
    6b 6b 6b 6b 00 a4 00 0c 02 e1 03 6b 6b 6b 6b 6b  kkkk.......kkkkk
    6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
  backtrace (crc 7c40cc2a):
    kmem_cache_alloc_node_noprof+0x492/0x630
    __alloc_skb+0x11e/0x5f0
    alloc_skb_with_frags+0xc6/0x8f0
    sock_alloc_send_pskb+0x326/0x3f0
    nfc_alloc_send_skb+0x94/0x1d0
    rawsock_sendmsg+0x162/0x4c0
    do_syscall_64+0x117/0xfc0

Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/nfc/nci/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index 6e9b76e2cc56..40fc397858ce 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -1035,18 +1035,23 @@ static int nci_transceive(struct nfc_dev *nfc_dev, struct nfc_target *target,
 	struct nci_conn_info *conn_info;
 
 	conn_info = ndev->rf_conn_info;
-	if (!conn_info)
+	if (!conn_info) {
+		kfree_skb(skb);
 		return -EPROTO;
+	}
 
 	pr_debug("target_idx %d, len %d\n", target->idx, skb->len);
 
 	if (!ndev->target_active_prot) {
 		pr_err("unable to exchange data, no active target\n");
+		kfree_skb(skb);
 		return -EINVAL;
 	}
 
-	if (test_and_set_bit(NCI_DATA_EXCHANGE, &ndev->flags))
+	if (test_and_set_bit(NCI_DATA_EXCHANGE, &ndev->flags)) {
+		kfree_skb(skb);
 		return -EBUSY;
+	}
 
 	/* store cb and context to be used on receiving data */
 	conn_info->data_exchange_cb = cb;
-- 
2.53.0