[Bluetooth] Fix L2CAP and HCI setsockopt() information leaks

The L2CAP and HCI setsockopt() implementations have a small information
leak that makes it possible to leak kernel stack memory to userspace.

If the optlen parameter is 0, no data will be copied by copy_from_user(),
but the uninitialized stack buffer will be read and stored later. A call
to getsockopt() can now retrieve the leaked information.

To fix this problem the stack buffer given to copy_from_user() must be
initialized with the current settings.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 832b5f44be5c..bfc9a35bad33 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -499,6 +499,15 @@ static int hci_sock_setsockopt(struct socket *sock, int level, int optname, char
                 break;
 
         case HCI_FILTER:
+                {
+                        struct hci_filter *f = &hci_pi(sk)->filter;
+
+                        uf.type_mask = f->type_mask;
+                        uf.opcode    = f->opcode;
+                        uf.event_mask[0] = *((u32 *) f->event_mask + 0);
+                        uf.event_mask[1] = *((u32 *) f->event_mask + 1);
+                }
+
                 len = min_t(unsigned int, len, sizeof(uf));
                 if (copy_from_user(&uf, optval, len)) {
                         err = -EFAULT;