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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+017a32f149406df32703@syzkaller.appspotmail.com,
        Myungho Jung <mhjungk@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>
Subject: [PATCH 4.14 19/41] Bluetooth: hci_uart: Check if socket buffer is ERR_PTR in h4_recv_buf()
Date:   Tue, 26 Mar 2019 15:29:56 +0900
Message-Id: <20190326042650.963542802@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Myungho Jung <mhjungk@gmail.com>

commit 1dc2d785156cbdc80806c32e8d2c7c735d0b4721 upstream.

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>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/bluetooth/hci_h4.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/bluetooth/hci_h4.c
+++ b/drivers/bluetooth/hci_h4.c
@@ -174,6 +174,10 @@ struct sk_buff *h4_recv_buf(struct hci_d
 	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;