[PATCH 4.19 256/306] Bluetooth: Fix invalid-free in bcsp_close()

[Greg Kroah-Hartman]

From: Tomas Bortoli <tomasbortoli@xxxxxxxxx>

commit cf94da6f502d8caecabd56b194541c873c8a7a3c upstream.

Syzbot reported an invalid-free that I introduced fixing a memleak.

bcsp_recv() also frees bcsp->rx_skb but never nullifies its value.
Nullify bcsp->rx_skb every time it is freed.

Signed-off-by: Tomas Bortoli <tomasbortoli@xxxxxxxxx>
Reported-by: syzbot+a0d209a4676664613e76@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/bluetooth/hci_bcsp.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/bluetooth/hci_bcsp.c
+++ b/drivers/bluetooth/hci_bcsp.c
@@ -606,6 +606,7 @@ static int bcsp_recv(struct hci_uart *hu
 			if (*ptr == 0xc0) {
 				BT_ERR("Short BCSP packet");
 				kfree_skb(bcsp->rx_skb);
+				bcsp->rx_skb = NULL;
 				bcsp->rx_state = BCSP_W4_PKT_START;
 				bcsp->rx_count = 0;
 			} else
@@ -621,6 +622,7 @@ static int bcsp_recv(struct hci_uart *hu
 			    bcsp->rx_skb->data[2])) != bcsp->rx_skb->data[3]) {
 				BT_ERR("Error in BCSP hdr checksum");
 				kfree_skb(bcsp->rx_skb);
+				bcsp->rx_skb = NULL;
 				bcsp->rx_state = BCSP_W4_PKT_DELIMITER;
 				bcsp->rx_count = 0;
 				continue;
@@ -645,6 +647,7 @@ static int bcsp_recv(struct hci_uart *hu
 				       bscp_get_crc(bcsp));
 
 				kfree_skb(bcsp->rx_skb);
+				bcsp->rx_skb = NULL;
 				bcsp->rx_state = BCSP_W4_PKT_DELIMITER;
 				bcsp->rx_count = 0;
 				continue;