linux-kernel - Re: [PATCH V2 4/4] misc: vop: mapping kernel memory to user space as noncached

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200929102833.GD7784@infradead.org>
Date:   Tue, 29 Sep 2020 11:28:33 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Sherry Sun <sherry.sun@....com>
Cc:     hch@...radead.org, sudeep.dutt@...el.com, ashutosh.dixit@...el.com,
        arnd@...db.de, gregkh@...uxfoundation.org, kishon@...com,
        lorenzo.pieralisi@....com, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH V2 4/4] misc: vop: mapping kernel memory to user space as
 noncached

On Tue, Sep 29, 2020 at 04:44:25PM +0800, Sherry Sun wrote:
> Mapping kernel space memory to user space as noncached, since user space
> need check the updates of avail_idx and device page flags timely.
> 
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> Signed-off-by: Sherry Sun <sherry.sun@....com>
> ---
>  drivers/misc/mic/vop/vop_vringh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/mic/vop/vop_vringh.c b/drivers/misc/mic/vop/vop_vringh.c
> index 4d5feb39aeb7..6e193bd64ef1 100644
> --- a/drivers/misc/mic/vop/vop_vringh.c
> +++ b/drivers/misc/mic/vop/vop_vringh.c
> @@ -1057,7 +1057,7 @@ static int vop_mmap(struct file *f, struct vm_area_struct *vma)
>  		}
>  		err = remap_pfn_range(vma, vma->vm_start + offset,
>  				      pa >> PAGE_SHIFT, size,
> -				      vma->vm_page_prot);
> +				      pgprot_noncached(vma->vm_page_prot));

You can't call remap_pfn_range on memory returned from
dma_alloc_coherent (which btw is not marked uncached on many platforms).

You need to use the dma_mmap_coherent helper instead.  And this also
needs to go into the first patch.