[PATCH] Bluetooth: hci_sock: validate event length before filtering

[Aldo Ariel Panzardo <qwe.aldo@gmail.com>]

is_filtered_packet() reads the event code from skb->data[0] without first
checking that the skb is nonempty. When an opcode filter is configured,
it also reads the command opcode at offsets 3 or 4 without checking that
a Command Complete or Command Status event is long enough.

hci_send_to_sock() invokes the filter before hci_event_packet() validates
the event header. A malformed event supplied by a controller or a vhci
device can therefore cause an out-of-bounds read.

Keep the unmasked event code for the opcode checks. The masked value is
needed for the 64-bit event bitmap, but using it to identify command events
aliases event codes above 0x3f. In particular, Synchronous Train Complete
(0x4f) was treated as Command Status (0x0f) even though its payload has no
opcode.

Reject actual command events that are too short for the field being
inspected. A truncated command event cannot match a configured opcode.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
---
 net/bluetooth/hci_sock.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 070ca388f..f6406dcec 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -164,6 +164,7 @@ static bool is_filtered_packet(struct sock *sk, struct sk_buff *skb)
 {
 	struct hci_filter *flt;
 	int flt_type, flt_event;
+	u8 event;
 
 	/* Apply filter */
 	flt = &hci_pi(sk)->filter;
@@ -177,7 +178,11 @@ static bool is_filtered_packet(struct sock *sk, struct sk_buff *skb)
 	if (hci_skb_pkt_type(skb) != HCI_EVENT_PKT)
 		return false;
 
-	flt_event = (*(__u8 *)skb->data & HCI_FLT_EVENT_BITS);
+	if (skb->len < 1)
+		return true;
+
+	event = *(__u8 *)skb->data;
+	flt_event = event & HCI_FLT_EVENT_BITS;
 
 	if (!hci_test_bit(flt_event, &flt->event_mask))
 		return true;
@@ -186,11 +191,17 @@ static bool is_filtered_packet(struct sock *sk, struct sk_buff *skb)
 	if (!flt->opcode)
 		return false;
 
-	if (flt_event == HCI_EV_CMD_COMPLETE &&
+	if (event == HCI_EV_CMD_COMPLETE && skb->len < 5)
+		return true;
+
+	if (event == HCI_EV_CMD_COMPLETE &&
 	    flt->opcode != get_unaligned((__le16 *)(skb->data + 3)))
 		return true;
 
-	if (flt_event == HCI_EV_CMD_STATUS &&
+	if (event == HCI_EV_CMD_STATUS && skb->len < 6)
+		return true;
+
+	if (event == HCI_EV_CMD_STATUS &&
 	    flt->opcode != get_unaligned((__le16 *)(skb->data + 4)))
 		return true;
 
-- 
2.43.0