linux-kernel - Re: [PATCH] arm64: mm: Fix memmap to be initialized for the entire section

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: <20161124134238.GI10776@rric.localdomain>
Date:   Thu, 24 Nov 2016 14:42:38 +0100
From:   Robert Richter <robert.richter@...ium.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:     Will Deacon <will.deacon@....com>,
        Robert Richter <rric@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        David Daney <david.daney@...ium.com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: mm: Fix memmap to be initialized for the entire
 section

On 23.11.16 21:25:06, Ard Biesheuvel wrote:
> Why? MEMREMAP_WB is used often, among other things for mapping
> firmware tables, which are marked as NOMAP, so in these cases, the
> linear address is not mapped.

If fw tables are mapped wb, that is wrong and needs a separate fix.

> > If you think pfn_valid() is wrong here, I am happy to send a patch
> > that fixes this by using page_is_ram(). In any case, the worst case
> > that may happen is to behave the same as v4.4, we might fix then the
> > wrong use of pfn_valid() where it is not correctly used to check for
> > ram.
> >
> 
> page_is_ram() uses string comparisons to look for regions called
> 'System RAM'. Is that something we can tolerate for each pfn_valid()
> calll?
> 
> Perhaps the solution is to reimplement page_is_ram() for arm64 using
> memblock_is_memory() instead, But that still means we need to modify
> the generic memremap() code first to switch to it before changing the
> arm64 implementation of pfn_valid

No, that's not the solution. pfn_valid() should just check if there is
a valid struct page, as other archs do. And if there is a mis-use of
pfn_valid() to check for ram, only that calls should be fixed to use
page_is_ram(), however this is implemented, or something appropriate.
But I don't see any problematic code, and if so, I will fix that.

-Robert