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    Subject[PATCH 5.15 188/917] Bluetooth: call sock_hold earlier in sco_conn_del
    Date
    From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>

    [ Upstream commit f4712fa993f688d0a48e0c28728fcdeb88c1ea58 ]

    In sco_conn_del, conn->sk is read while holding on to the
    sco_conn.lock to avoid races with a socket that could be released
    concurrently.

    However, in between unlocking sco_conn.lock and calling sock_hold,
    it's possible for the socket to be freed, which would cause a
    use-after-free write when sock_hold is finally called.

    To fix this, the reference count of the socket should be increased
    while the sco_conn.lock is still held.

    Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
    Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/bluetooth/sco.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
    index b62c91c627e2c..4a057f99b60aa 100644
    --- a/net/bluetooth/sco.c
    +++ b/net/bluetooth/sco.c
    @@ -187,10 +187,11 @@ static void sco_conn_del(struct hci_conn *hcon, int err)
    /* Kill socket */
    sco_conn_lock(conn);
    sk = conn->sk;
    + if (sk)
    + sock_hold(sk);
    sco_conn_unlock(conn);

    if (sk) {
    - sock_hold(sk);
    lock_sock(sk);
    sco_sock_clear_timer(sk);
    sco_chan_del(sk, err);
    --
    2.33.0


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