linux-kernel - Re: Crash in -next due to 'mm/vmalloc: replace opencoded 4-level page walkers'

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] [day] [month] [year] [list]

Date:   Mon, 09 Jan 2017 14:48:59 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     chris@...is-wilson.co.uk
Cc:     linux@...ck-us.net, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: Crash in -next due to 'mm/vmalloc: replace opencoded 4-level
 page walkers'

From: Chris Wilson <chris@...is-wilson.co.uk>
Date: Mon, 9 Jan 2017 11:37:07 +0000

> Could some mm expert explain why it is safe for mm/vmalloc.c to ignore
> huge pud/pmd that raise BUG_ON in the same code in mm/memory.c
> (vmap_pmd_range() vs apply_to_pmd_range())?
> 
> At a guess, is sparc64 covering the init_mm with a huge zero page? How
> is it then meant to be split? Something like

We map the linear physical area (PAGE_OFFSET --> PAGE_OFFSET +
max_phys_addr) using huge pages unless DEBUG_PAGEALLOC is enabled.

It is not meant to be split, and that's why we don't use huge pages
when DEBUG_PAGEALLOC is set since that requires changes to the mapping
to be possible.