linux-kernel - Re: [PATCH] iommu/iova: Don't BUG on invalid PFNs

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Message-ID: <20200630084251.GA28824@8bytes.org>
Date:   Tue, 30 Jun 2020 10:42:51 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Prakash Gupta <guptap@...eaurora.org>
Subject: Re: [PATCH] iommu/iova: Don't BUG on invalid PFNs

On Tue, Jun 02, 2020 at 02:08:18PM +0100, Robin Murphy wrote:
> Unlike the other instances which represent a complete loss of
> consistency within the rcache mechanism itself, or a fundamental
> and obvious misconfiguration by an IOMMU driver, the BUG_ON() in
> iova_magazine_free_pfns() can be provoked at more or less any time
> in a "spooky action-at-a-distance" manner by any old device driver
> passing nonsense to dma_unmap_*() which then propagates through to
> queue_iova().
> 
> Not only is this well outside the IOVA layer's control, it's also
> nowhere near fatal enough to justify panicking anyway - all that
> really achieves is to make debugging the offending driver more
> difficult. Let's simply WARN and otherwise ignore bogus PFNs.
> 
> Reported-by: Prakash Gupta <guptap@...eaurora.org>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
>  drivers/iommu/iova.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Applied without stable tag, thanks.