linux-kernel - Re: [PATCH 3/5] mm/swap_state: fix get_shadow_from_swap

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: <87im4rufwq.fsf@yhuang6-desk1.ccr.corp.intel.com>
Date:   Tue, 13 Apr 2021 09:33:41 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     <akpm@...ux-foundation.org>, <hannes@...xchg.org>,
        <mhocko@...e.com>, <iamjoonsoo.kim@....com>, <vbabka@...e.cz>,
        <alex.shi@...ux.alibaba.com>, <willy@...radead.org>,
        <minchan@...nel.org>, <richard.weiyang@...il.com>,
        <hughd@...gle.com>, <tim.c.chen@...ux.intel.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH 3/5] mm/swap_state: fix get_shadow_from_swap_cache()
 race with swapoff

Miaohe Lin <linmiaohe@...wei.com> writes:

> The function get_shadow_from_swap_cache() can race with swapoff, though
> it's only called by do_swap_page() now.
>
> Fixes: aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU")
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

This is unnecessary.  The only caller has guaranteed the swap device
from swapoff.

Best Regards,
Huang, Ying

> ---
>  mm/swap_state.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 272ea2108c9d..709c260d644a 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -83,11 +83,14 @@ void show_swap_cache_info(void)
>  
>  void *get_shadow_from_swap_cache(swp_entry_t entry)
>  {
> -	struct address_space *address_space = swap_address_space(entry);
> -	pgoff_t idx = swp_offset(entry);
> +	struct swap_info_struct *si;
>  	struct page *page;
>  
> -	page = xa_load(&address_space->i_pages, idx);
> +	si = get_swap_device(entry);
> +	if (!si)
> +		return NULL;
> +	page = xa_load(&swap_address_space(entry)->i_pages, swp_offset(entry));
> +	put_swap_device(si);
>  	if (xa_is_value(page))
>  		return page;
>  	return NULL;