Date:   Tue, 22 Jan 2019 00:33:26 -0800
From:   Myungho Jung <mhjungk@gmail.com>
To:     Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>
Cc:     linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] Bluetooth: hci_uart: Check if socket buffer is ERR_PTR in
 h4_recv_buf()
Message-ID: <20190122083323.GA22508@myunghoj-Precision-5530>
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User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-bluetooth-owner@vger.kernel.org
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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@syzkaller.appspotmail.com
Signed-off-by: Myungho Jung <mhjungk@gmail.com>
---
 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..285cf72190b7 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 if socket buffer is not reset yet from previous error */
+	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..dea48090d2dc 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 if socket buffer is not reset yet from previous error */
+	if (IS_ERR(skb))
+		skb = NULL;
+
 	while (count) {
 		int i, len;
 
-- 
2.17.1