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/ae5be371a9f53fed33d2b34748a95a5498fd4b...

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 --- net/bluetooth/l2cap_sock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index 49f97d4138ea..46ea0bee2259 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -710,12 +710,12 @@ 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; }