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    Subject[PATCH 6.0 336/862] net: rds: dont hold sock lock when cancelling work from rds_tcp_reset_callbacks()
    Date
    From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

    [ Upstream commit a91b750fd6629354460282bbf5146c01b05c4859 ]

    syzbot is reporting lockdep warning at rds_tcp_reset_callbacks() [1], for
    commit ac3615e7f3cffe2a ("RDS: TCP: Reduce code duplication in
    rds_tcp_reset_callbacks()") added cancel_delayed_work_sync() into a section
    protected by lock_sock() without realizing that rds_send_xmit() might call
    lock_sock().

    We don't need to protect cancel_delayed_work_sync() using lock_sock(), for
    even if rds_{send,recv}_worker() re-queued this work while __flush_work()
    from cancel_delayed_work_sync() was waiting for this work to complete,
    retried rds_{send,recv}_worker() is no-op due to the absence of RDS_CONN_UP
    bit.

    Link: https://syzkaller.appspot.com/bug?extid=78c55c7bc6f66e53dce2 [1]
    Reported-by: syzbot <syzbot+78c55c7bc6f66e53dce2@syzkaller.appspotmail.com>
    Co-developed-by: Hillf Danton <hdanton@sina.com>
    Signed-off-by: Hillf Danton <hdanton@sina.com>
    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Tested-by: syzbot <syzbot+78c55c7bc6f66e53dce2@syzkaller.appspotmail.com>
    Fixes: ac3615e7f3cffe2a ("RDS: TCP: Reduce code duplication in rds_tcp_reset_callbacks()")
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/rds/tcp.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/net/rds/tcp.c b/net/rds/tcp.c
    index 73ee2771093d..d0ff413f697c 100644
    --- a/net/rds/tcp.c
    +++ b/net/rds/tcp.c
    @@ -166,10 +166,10 @@ void rds_tcp_reset_callbacks(struct socket *sock,
    */
    atomic_set(&cp->cp_state, RDS_CONN_RESETTING);
    wait_event(cp->cp_waitq, !test_bit(RDS_IN_XMIT, &cp->cp_flags));
    - lock_sock(osock->sk);
    /* reset receive side state for rds_tcp_data_recv() for osock */
    cancel_delayed_work_sync(&cp->cp_send_w);
    cancel_delayed_work_sync(&cp->cp_recv_w);
    + lock_sock(osock->sk);
    if (tc->t_tinc) {
    rds_inc_put(&tc->t_tinc->ti_inc);
    tc->t_tinc = NULL;
    --
    2.35.1


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