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Date:   Tue, 5 Jul 2022 15:06:49 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Dan Carpenter <dan.carpenter@oracle.com>
Cc:     Longfang Liu <liulongfang@huawei.com>,
        Yishai Hadas <yishaih@nvidia.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] vfio: hisi_acc_vfio_pci: fix integer overflow check in
 hisi_acc_vf_resume_write()
Message-ID: <20220705180649.GI23621@ziepe.ca>
References: <YsP+2CWqMudArkqF@kili>
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On Tue, Jul 05, 2022 at 12:05:28PM +0300, Dan Carpenter wrote:
> The casting on this makes the integer overflow check slightly wrong.
> "len" is an unsigned long. "*pos" and "requested_length" are signed
> long longs.  Imagine "len" is ULONG_MAX and "*pos" is 2.
> "ULONG_MAX + 2 = 1". 

I wonder if this can happen, len is a kernel controlled value bounded
by a memory allocation..

> Fixes: b0eed085903e ("hisi_acc_vfio_pci: Add support for VFIO live migration")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---

This code was copy and pasted from drivers/vfio/pci/mlx5/main.c, so it
should be fixed too

> It is strange that we are doing:
> 
> 	pos = &filp->f_pos;
>
> instead of using the passed in value of pos.  

IIRC the way we have the struct file configured the pos argument is
NULL.

Jason