Re: [PATCH 3/9] IB: add a helper to safely drain a QP

[Sagi Grimberg]

On 17/11/2015 19:06, Bart Van Assche wrote:
> On 11/15/2015 01:34 AM, Sagi Grimberg wrote:
> > This is taken from srp, and srp drains using a recv wr due to a race
> > causing a use-after-free condition in srp which re-posts a recv buffer
> > in the recv completion handler.
>
> Hello Sagi,
>
> Would it be possible to clarify this ? Does this refer to an existing
> race or a race that would only occur if the code would be modified ?

I was referring to a bug that srp_destroy_qp() was design to
address:

commit 7dad6b2e440d810273946b0e7092a8fe043c3b8a
Author: Bart Van Assche <bvanassche@xxxxxxx>
Date:   Tue Oct 21 18:00:35 2014 +0200

    IB/srp: Fix a race condition triggered by destroying a queue pair

    At least LID reassignment can trigger a race condition in the SRP
    initiator driver, namely the receive completion handler trying to
    post a request on a QP during or after QP destruction and before
    the CQ's have been destroyed. Avoid this race by modifying a QP
    into the error state and by waiting until all receive completions
    have been processed before destroying a QP.

    Reported-by: Max Gurtuvoy <maxg@xxxxxxxxxxxx>
    Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
    Reviewed-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
    Signed-off-by: Christoph Hellwig <hch@xxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/