linux-kernel - Re: [PATCH] mm: skip checking poison pattern for page_to

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20181219102010.GF5758@dhcp22.suse.cz>
Date:   Wed, 19 Dec 2018 11:20:10 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     akpm@...ux-foundation.org, mingo@...nel.org, hpa@...or.com,
        mgorman@...hsingularity.net, tglx@...utronix.de,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: skip checking poison pattern for page_to_nid()

On Tue 18-12-18 20:57:32, Qian Cai wrote:
[...]
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5411de93a363..f083f366ea90 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -985,9 +985,7 @@ extern int page_to_nid(const struct page *page);
>  #else
>  static inline int page_to_nid(const struct page *page)
>  {
> -	struct page *p = (struct page *)page;
> -
> -	return (PF_POISONED_CHECK(p)->flags >> NODES_PGSHIFT) & NODES_MASK;
> +	return (page->flags >> NODES_PGSHIFT) & NODES_MASK;
>  }
>  #endif

I didn't get to think about a proper fix but this is clearly worng. If
the page is still poisoned then flags are clearly bogus and the node you
get is a garbage as well. Have you actually tested this patch?
-- 
Michal Hocko
SUSE Labs