linux-kernel - Re: [PATCH 08/14] mm/hmm: cleanup special vma handling (VM

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: <44d08350-7035-a26c-d6c8-29b3dc3f99eb@nvidia.com>
Date:   Fri, 16 Mar 2018 21:35:29 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     <jglisse@...hat.com>, <linux-mm@...ck.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>,
        Evgeny Baskakov <ebaskakov@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Mark Hairgrove <mhairgrove@...dia.com>
Subject: Re: [PATCH 08/14] mm/hmm: cleanup special vma handling (VM_SPECIAL)

On 03/16/2018 12:14 PM, jglisse@...hat.com wrote:
> From: Jérôme Glisse <jglisse@...hat.com>
> 
> Special vma (one with any of the VM_SPECIAL flags) can not be access by
> device because there is no consistent model accross device drivers on
> those vma and their backing memory.
> 
> This patch directly use hmm_range struct for hmm_pfns_special() argument
> as it is always affecting the whole vma and thus the whole range.
> 
> It also make behavior consistent after this patch both hmm_vma_fault()
> and hmm_vma_get_pfns() returns -EINVAL when facing such vma. Previously
> hmm_vma_fault() returned 0 and hmm_vma_get_pfns() return -EINVAL but
> both were filling the HMM pfn array with special entry.
> 

Hi Jerome,

This seems correct. 

<snip>

> @@ -486,6 +478,14 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
>  	return 0;
>  }
>  
> +static void hmm_pfns_special(struct hmm_range *range)
> +{
> +	unsigned long addr = range->start, i = 0;
> +
> +	for (; addr < range->end; addr += PAGE_SIZE, i++)
> +		range->pfns[i] = HMM_PFN_SPECIAL;
> +}

Silly nit: the above would read more naturally, like this:

	unsigned long addr, i = 0;

	for (addr = range->start; addr < range->end; addr += PAGE_SIZE, i++)
		range->pfns[i] = HMM_PFN_SPECIAL;

Either way,

Reviewed-by: John Hubbard <jhubbard@...dia.com>

thanks,
-- 
John Hubbard
NVIDIA