linux-kernel - Re: [RFC 0/3] iommu/iova: Unsafe locking in find

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Message-ID: <20180706131611.h3w2kdinmjguikgo@8bytes.org>
Date:   Fri, 6 Jul 2018 15:16:11 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org,
        David Woodhouse <dwmw2@...radead.org>,
        iommu@...ts.linux-foundation.org,
        Dmitry Safonov <0x7f454c46@...il.com>
Subject: Re: [RFC 0/3] iommu/iova: Unsafe locking in find_iova()

On Thu, Jun 21, 2018 at 07:08:20PM +0100, Dmitry Safonov wrote:
> find_iova() looks to be using a bad locking practice: it locks the
> returned iova only for the search time.  And looking in code, the
> element can be removed from the tree and freed under rbtree lock. That
> happens during memory hot-unplug and cleanup on module removal.  Here
> I cleanup users of the function and delete it.

But this is only a problem if more than one code-path uses tries to
handle a given iova at the same time, no?

Regards,

	Joerg