From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Date: Thu, 23 Feb 2017 09:31:18 -0300
> commit 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
> attempted to avoid a BUG_ON call when the association being used for a
> sendmsg() is blocked waiting for more sndbuf and another thread did a
> peeloff operation on such asoc, moving it to another socket.
>
> As Ben Hutchings noticed, then in such case it would return without
> locking back the socket and would cause two unlocks in a row.
>
> Further analysis also revealed that it could allow a double free if the
> application managed to peeloff the asoc that is created during the
> sendmsg call, because then sctp_sendmsg() would try to free the asoc
> that was created only for that call.
>
> This patch takes another approach. It will deny the peeloff operation
> if there is a thread sleeping on the asoc, so this situation doesn't
> exist anymore. This avoids the issues described above and also honors
> the syscalls that are already being handled (it can be multiple sendmsg
> calls).
>
> Joint work with Xin Long.
>
> Fixes: 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
> Cc: Alexander Popov <alex.popov@xxxxxxxxx>
> Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> Hi, please consider this one for -stable too. Thanks
Applied and queued up for -stable, thanks.
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