linux-kernel - Re: [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON

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Message-ID: <20200117095953.GB15760@8bytes.org>
Date:   Fri, 17 Jan 2020 10:59:54 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     ashok.raj@...el.com, jacob.jun.pan@...el.com, kevin.tian@...el.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

On Thu, Jan 16, 2020 at 09:52:36AM +0800, Lu Baolu wrote:
> Address field in device TLB invalidation descriptor is qualified
> by the S field. If S field is zero, a single page at page address
> specified by address [63:12] is requested to be invalidated. If S
> field is set, the least significant bit in the address field with
> value 0b (say bit N) indicates the invalidation address range. The
> spec doesn't require the address [N - 1, 0] to be cleared, hence
> remove the unnecessary WARN_ON_ONCE().
> 
> Otherwise, the caller might set "mask = MAX_AGAW_PFN_WIDTH" in order
> to invalidating all the cached mappings on an endpoint, and below
> overflow error will be triggered.
> 
> [...]
> UBSAN: Undefined behaviour in drivers/iommu/dmar.c:1354:3
> shift exponent 64 is too large for 64-bit type 'long long unsigned int'
> [...]
> 
> Reported-and-tested-by: Frank <fgndev@...teo.de>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

Does this need a Fixes and/or stable tag?


Regards,

	Joerg