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From: Joerg Roedel <joro@8bytes.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	Prakash Gupta <guptap@codeaurora.org>
Subject: Re: [PATCH] iommu/iova: Don't BUG on invalid PFNs
Date: Tue, 30 Jun 2020 10:42:51 +0200	[thread overview]
Message-ID: <20200630084251.GA28824@8bytes.org> (raw)
In-Reply-To: <acbd2d092b42738a03a21b417ce64e27f8c91c86.1591103298.git.robin.murphy@arm.com>

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@codeaurora.org>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/iommu/iova.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Applied without stable tag, thanks.

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WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	Prakash Gupta <guptap@codeaurora.org>
Subject: Re: [PATCH] iommu/iova: Don't BUG on invalid PFNs
Date: Tue, 30 Jun 2020 10:42:51 +0200	[thread overview]
Message-ID: <20200630084251.GA28824@8bytes.org> (raw)
In-Reply-To: <acbd2d092b42738a03a21b417ce64e27f8c91c86.1591103298.git.robin.murphy@arm.com>

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@codeaurora.org>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/iommu/iova.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Applied without stable tag, thanks.


  parent reply	other threads:[~2020-06-30  8:43 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-02 13:08 [PATCH] iommu/iova: Don't BUG on invalid PFNs Robin Murphy
2020-06-02 13:08 ` Robin Murphy
2020-06-10  9:27 ` guptap
2020-06-10  9:27   ` guptap
2020-06-10 10:12   ` Robin Murphy
2020-06-10 10:12     ` Robin Murphy
2020-06-30  8:42 ` Joerg Roedel [this message]
2020-06-30  8:42   ` Joerg Roedel

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