linux-kernel - Re: [Xen-devel] [PATCH v2 3/3] xen/swiotlb: remember having called xen_create_contiguous

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: <55b35087-064d-8188-2373-0dd94ffef2b6@suse.com>
Date:   Wed, 29 May 2019 12:21:41 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <JBeulich@...e.com>
Cc:     Stefano Stabellini <sstabellini@...nel.org>,
        iommu@...ts.linux-foundation.org,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH v2 3/3] xen/swiotlb: remember having called
 xen_create_contiguous_region()

On 29/05/2019 11:57, Jan Beulich wrote:
>>>> On 29.05.19 at 11:04, <jgross@...e.com> wrote:
>> @@ -345,8 +346,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>>  	size = 1UL << (order + XEN_PAGE_SHIFT);
>>  
>>  	if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
>> -		     range_straddles_page_boundary(phys, size)))
>> +		     range_straddles_page_boundary(phys, size)) &&
>> +	    PageXenRemapped(virt_to_page(vaddr))) {
>>  		xen_destroy_contiguous_region(phys, order);
>> +		ClearPageXenRemapped(virt_to_page(vaddr));
>> +	}
> 
> To be symmetric with setting the flag only after having made the region
> contiguous, and to avoid (perhaps just theoretical) races, wouldn't it be
> better to clear the flag before calling xen_destroy_contiguous_region()?
> Even better would be a TestAndClear...() operation.

I like that idea.


Juergen