netdev - Re: [PATCH net] sctp: hold the transport before using it in sctp_hash

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Date:   Fri, 9 Sep 2016 15:24:17 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Neil Horman <nhorman@...driver.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem <davem@...emloft.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Vlad Yasevich <vyasevich@...il.com>, daniel@...earbox.net
Subject: Re: [PATCH net] sctp: hold the transport before using it in sctp_hash_cmp

>>
> What path does this occur in?  __sctp_lookup_association takes a hold on the
> asoc, and that function is protected by the rcu_read_lock, so I'm not sure how
> you get into a situation in which the asoc can be deleted while the lookup is
> occuring.
>
yes  that function is protected by the rcu_read_lock, it can only
ensure sctp_transport_destroy_rcu will NOT be called. But,
sctp_transport_destroy can be called by sctp_assocation_free.
in which, sctp free and unhash  all the transport. when transport's
defcnt become 0, sctp will call sctp_transport_destroy, in which,
asoc can be destroyed because of:
if (transport->asoc)
        sctp_association_put(transport->asoc);