linux-kernel - Re: [netfilter-core] kernel panic: Out of memory and no killable processes... (2)

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Message-ID: <20180207174439.esm4djxb4trbotne@salvia>
Date:   Wed, 7 Feb 2018 18:44:39 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Yang Shi <yang.s@...baba-inc.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        netdev <netdev@...r.kernel.org>, guro@...com,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        syzkaller-bugs@...glegroups.com, Linux-MM <linux-mm@...ck.org>,
        coreteam@...filter.org, netfilter-devel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        David Miller <davem@...emloft.net>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [netfilter-core] kernel panic: Out of memory and no killable
 processes... (2)

Hi,

On Wed, Jan 31, 2018 at 09:19:16AM +0100, Michal Hocko wrote:
[...]
> Yeah, we do not BUG but rather fail instead. See __vmalloc_node_range.
> My excavation tools pointed me to "VM: Rework vmalloc code to support mapping of arbitray pages"
> by Christoph back in 2002. So yes, we can safely remove it finally. Se
> below.
> 
> 
> From 8d52e1d939d101b0dafed6ae5c3c1376183e65bb Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@...e.com>
> Date: Wed, 31 Jan 2018 09:16:56 +0100
> Subject: [PATCH] net/netfilter/x_tables.c: remove size check
> 
> Back in 2002 vmalloc used to BUG on too large sizes. We are much better
> behaved these days and vmalloc simply returns NULL for those. Remove
> the check as it simply not needed and the comment even misleading.
> 
> Suggested-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Michal Hocko <mhocko@...e.com>
> ---
>  net/netfilter/x_tables.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index b55ec5aa51a6..48a6ff620493 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -999,10 +999,6 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
>  	if (sz < sizeof(*info))
>  		return NULL;
>  
> -	/* Pedantry: prevent them from hitting BUG() in vmalloc.c --RR */
> -	if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages)
> -		return NULL;
> -
>  	/* __GFP_NORETRY is not fully supported by kvmalloc but it should
>  	 * work reasonably well if sz is too large and bail out rather
>  	 * than shoot all processes down before realizing there is nothing

Patchwork didn't catch this patch for some reason, would you mind to
resend?

Thanks!