From: Johan Hedberg <johan.hedberg@xxxxxxxxx>
The l2cap_recv_frame function is expected to take ownership and
eventually free the skb passed to it. We need to ensure that the
conn->rx_skb pointer is no longer reachable when calling
l2cap_recv_frame so that no other function, such as l2cap_conn_del, may
think that it can free conn->rx_skb.
An actual situation when this can happen is when smp_sig_channel (called
from l2cap_recv_frame) fails and l2cap_conn_del gets called as a
consequence. The l2cap_conn_del function would then try to free
conn->rx_skb, but as the same skb was just passed to smp_sig_channel and
freed we get a double-free.
Signed-off-by: Johan Hedberg <johan.hedberg@xxxxxxxxx>
---
net/bluetooth/l2cap_core.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index a9a7df6..06e7173 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -6798,9 +6798,13 @@ int l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
conn->rx_len -= skb->len;
if (!conn->rx_len) {
- /* Complete frame received */
- l2cap_recv_frame(conn, conn->rx_skb);
+ /* Complete frame received. l2cap_recv_frame
+ * takes ownership of the skb so set the global
+ * rx_skb pointer to NULL first.
+ */
+ struct sk_buff *rx_skb = conn->rx_skb;
conn->rx_skb = NULL;
+ l2cap_recv_frame(conn, rx_skb);
}
break;
}
--
1.8.3.1
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