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From: guptap@codeaurora.org
To: Robin Murphy <robin.murphy@arm.com>
Cc: iommu@lists.linux-foundation.org, stable@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/iova: Don't BUG on invalid PFNs
Date: Wed, 10 Jun 2020 14:57:00 +0530	[thread overview]
Message-ID: <79df62c92cf61f2b5f717c28d620a283@codeaurora.org> (raw)
In-Reply-To: <acbd2d092b42738a03a21b417ce64e27f8c91c86.1591103298.git.robin.murphy@arm.com>

On 2020-06-02 18:38, 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(-)
> 

Copying stable@vger.kernel.org

You can add
Reviewed-by: Prakash Gupta <guptap@codeaurora.org>

> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 0e6a9536eca6..612cbf668adf 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -811,7 +811,9 @@ iova_magazine_free_pfns(struct iova_magazine *mag,
> struct iova_domain *iovad)
>  	for (i = 0 ; i < mag->size; ++i) {
>  		struct iova *iova = private_find_iova(iovad, mag->pfns[i]);
> 
> -		BUG_ON(!iova);
> +		if (WARN_ON(!iova))
> +			continue;
> +
>  		private_free_iova(iovad, iova);
>  	}
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WARNING: multiple messages have this Message-ID (diff)
From: guptap@codeaurora.org
To: Robin Murphy <robin.murphy@arm.com>
Cc: joro@8bytes.org, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] iommu/iova: Don't BUG on invalid PFNs
Date: Wed, 10 Jun 2020 14:57:00 +0530	[thread overview]
Message-ID: <79df62c92cf61f2b5f717c28d620a283@codeaurora.org> (raw)
In-Reply-To: <acbd2d092b42738a03a21b417ce64e27f8c91c86.1591103298.git.robin.murphy@arm.com>

On 2020-06-02 18:38, 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(-)
> 

Copying stable@vger.kernel.org

You can add
Reviewed-by: Prakash Gupta <guptap@codeaurora.org>

> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 0e6a9536eca6..612cbf668adf 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -811,7 +811,9 @@ iova_magazine_free_pfns(struct iova_magazine *mag,
> struct iova_domain *iovad)
>  	for (i = 0 ; i < mag->size; ++i) {
>  		struct iova *iova = private_find_iova(iovad, mag->pfns[i]);
> 
> -		BUG_ON(!iova);
> +		if (WARN_ON(!iova))
> +			continue;
> +
>  		private_free_iova(iovad, iova);
>  	}

  reply	other threads:[~2020-06-10  9:27 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 [this message]
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
2020-06-30  8:42   ` Joerg Roedel

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