linux-kernel - Re: [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized memmaps in memory

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Message-ID: <20191009144323.GH6681@dhcp22.suse.cz>
Date:   Wed, 9 Oct 2019 16:43:23 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized
 memmaps in memory_failure()

On Wed 09-10-19 16:24:35, David Hildenbrand wrote:
> We should check for pfn_to_online_page() to not access uninitialized
> memmaps. Reshuffle the code so we don't have to duplicate the error
> message.
> 
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/memory-failure.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 7ef849da8278..e866e6e5660b 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1253,17 +1253,19 @@ int memory_failure(unsigned long pfn, int flags)
>  	if (!sysctl_memory_failure_recovery)
>  		panic("Memory failure on page %lx", pfn);
>  
> -	if (!pfn_valid(pfn)) {
> +	p = pfn_to_online_page(pfn);
> +	if (!p) {
> +		if (pfn_valid(pfn)) {
> +			pgmap = get_dev_pagemap(pfn, NULL);
> +			if (pgmap)
> +				return memory_failure_dev_pagemap(pfn, flags,
> +								  pgmap);
> +		}
>  		pr_err("Memory failure: %#lx: memory outside kernel control\n",
>  			pfn);
>  		return -ENXIO;

Don't we need that earlier at hwpoison_inject level?

-- 
Michal Hocko
SUSE Labs