Bluetooth: L2CAP: accept zero as a special value for MTU auto-selection

commit 5c61419e02033eaf01733d66e2fcd4044808f482 upstream.

One of the possible ways to enable the input MTU auto-selection for L2CAP
connections is supposed to be through passing a special "0" value for it
as a socket option. Commit [1] added one of those into avdtp. However, it
simply wouldn't work because the kernel still treats the specified value
as invalid and denies the setting attempt. Recorded BlueZ logs include the
following:

  bluetoothd[496]: profiles/audio/avdtp.c:l2cap_connect() setsockopt(L2CAP_OPTIONS): Invalid argument (22)

[1]: https://github.com/bluez/bluez/commit/ae5be371a9f53fed33d2b34748a95a5498fd4b77

Found by Linux Verification Center (linuxtesting.org).

Fixes: 4b6e228e297b ("Bluetooth: Auto tune if input MTU is set to 0")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 50b90b938dc6aa0696fb4d9a13618f1b8a059538..49564c61ad4a14eb5c96e39a63306b1b552e69a9 100644 (file)
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -727,12 +727,12 @@ static bool l2cap_valid_mtu(struct l2cap_chan *chan, u16 mtu)
 {
        switch (chan->scid) {
        case L2CAP_CID_ATT:
-               if (mtu < L2CAP_LE_MIN_MTU)
+               if (mtu && mtu < L2CAP_LE_MIN_MTU)
                        return false;
                break;
 
        default:
-               if (mtu < L2CAP_DEFAULT_MIN_MTU)
+               if (mtu && mtu < L2CAP_DEFAULT_MIN_MTU)
                        return false;
        }