[PATCH AUTOSEL 4.19 166/192] Bluetooth: hci_uart: Check if socket buffer is ERR_PTR in h4_recv_buf()

[Sasha Levin]

From: Myungho Jung <mhjungk@xxxxxxxxx>

[ Upstream commit 1dc2d785156cbdc80806c32e8d2c7c735d0b4721 ]

h4_recv_buf() callers store the return value to socket buffer and
recursively pass the buffer to h4_recv_buf() without protection. So,
ERR_PTR returned from h4_recv_buf() can be dereferenced, if called again
before setting the socket buffer to NULL from previous error. Check if
skb is ERR_PTR in h4_recv_buf().

Reported-by: syzbot+017a32f149406df32703@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Myungho Jung <mhjungk@xxxxxxxxx>
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/bluetooth/h4_recv.h | 4 ++++
 drivers/bluetooth/hci_h4.c  | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/bluetooth/h4_recv.h b/drivers/bluetooth/h4_recv.h
index b432651f8236..307d82166f48 100644
--- a/drivers/bluetooth/h4_recv.h
+++ b/drivers/bluetooth/h4_recv.h
@@ -60,6 +60,10 @@ static inline struct sk_buff *h4_recv_buf(struct hci_dev *hdev,
 					  const struct h4_recv_pkt *pkts,
 					  int pkts_count)
 {
+	/* Check for error from previous call */
+	if (IS_ERR(skb))
+		skb = NULL;
+
 	while (count) {
 		int i, len;
 
diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
index fb97a3bf069b..5d97d77627c1 100644
--- a/drivers/bluetooth/hci_h4.c
+++ b/drivers/bluetooth/hci_h4.c
@@ -174,6 +174,10 @@ struct sk_buff *h4_recv_buf(struct hci_dev *hdev, struct sk_buff *skb,
 	struct hci_uart *hu = hci_get_drvdata(hdev);
 	u8 alignment = hu->alignment ? hu->alignment : 1;
 
+	/* Check for error from previous call */
+	if (IS_ERR(skb))
+		skb = NULL;
+
 	while (count) {
 		int i, len;
 
-- 
2.19.1