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    Subject[PATCH 6.0 293/862] Bluetooth: RFCOMM: Fix possible deadlock on socket shutdown/release
    Date
    From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

    [ Upstream commit 812e92b824c1db16c9519f8624d48a9901a0d38f ]

    Due to change to switch to use lock_sock inside rfcomm_sk_state_change
    the socket shutdown/release procedure can cause a deadlock:

    rfcomm_sock_shutdown():
    lock_sock();
    __rfcomm_sock_close():
    rfcomm_dlc_close():
    __rfcomm_dlc_close():
    rfcomm_dlc_lock();
    rfcomm_sk_state_change():
    lock_sock();

    To fix this when the call __rfcomm_sock_close is now done without
    holding the lock_sock since rfcomm_dlc_lock exists to protect
    the dlc data there is no need to use lock_sock in that code path.

    Link: https://lore.kernel.org/all/CAD+dNTsbuU4w+Y_P7o+VEN7BYCAbZuwZx2+tH+OTzCdcZF82YA@mail.gmail.com/
    Fixes: b7ce436a5d79 ("Bluetooth: switch to lock_sock in RFCOMM")
    Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/bluetooth/rfcomm/sock.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
    index 4bf4ea6cbb5e..21e24da4847f 100644
    --- a/net/bluetooth/rfcomm/sock.c
    +++ b/net/bluetooth/rfcomm/sock.c
    @@ -902,7 +902,10 @@ static int rfcomm_sock_shutdown(struct socket *sock, int how)
    lock_sock(sk);
    if (!sk->sk_shutdown) {
    sk->sk_shutdown = SHUTDOWN_MASK;
    +
    + release_sock(sk);
    __rfcomm_sock_close(sk);
    + lock_sock(sk);

    if (sock_flag(sk, SOCK_LINGER) && sk->sk_lingertime &&
    !(current->flags & PF_EXITING))
    --
    2.35.1


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