linux-kernel - Re: [PATCH] iommu/arm-smmu-v3: Fix size calculation in arm_smmu_mm_invalidate

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Message-ID: <20220419231034.GP64706@ziepe.ca>
Date:   Tue, 19 Apr 2022 20:10:34 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Nicolin Chen <nicolinc@...dia.com>
Cc:     will@...nel.org, robin.murphy@....com, joro@...tes.org,
        jean-philippe@...aro.org, jacob.jun.pan@...ux.intel.com,
        baolu.lu@...ux.intel.com, fenghua.yu@...el.com,
        rikard.falkeborn@...il.com, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] iommu/arm-smmu-v3: Fix size calculation in
 arm_smmu_mm_invalidate_range()

On Tue, Apr 19, 2022 at 02:01:58PM -0700, Nicolin Chen wrote:
> The arm_smmu_mm_invalidate_range function is designed to be called
> by mm core for Shared Virtual Addressing purpose between IOMMU and
> CPU MMU. However, the ways of two subsystems defining their "end"
> addresses are slightly different. IOMMU defines its "end" address
> using the last address of an address range, while mm core defines
> that using the following address of an address range:
> 
> 	include/linux/mm_types.h:
> 		unsigned long vm_end;
> 		/* The first byte after our end address ...
> 
> This mismatch resulted in an incorrect calculation for size so it
> failed to be page-size aligned. Further, it caused a dead loop at
> "while (iova < end)" check in __arm_smmu_tlb_inv_range function.
> 
> This patch fixes the issue by doing the calculation correctly.
> 
> Fixes: 2f7e8c553e98d ("iommu/arm-smmu-v3: Hook up ATC invalidation to mm ops")
> Cc: stable@...r.kernel.org
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

> -	size_t size = end - start + 1;
> +	size_t size;
> +
> +	/*
> +	 * The mm_types defines vm_end as the first byte after the end address,
> +	 * different from IOMMU subsystem using the last address of an address
> +	 * range. So do a simple translation here by calculating size correctly.
> +	 */
> +	size = end - start;

I would skip the comment though

Jason