From: Yu Zhao <yuzhao@google.com>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Huang Ying <ying.huang@intel.com>,
dennis@kernel.org, Tim Chen <tim.c.chen@linux.intel.com>,
Hugh Dickins <hughd@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
alexs@kernel.org, Matthew Wilcox <willy@infradead.org>,
Minchan Kim <minchan@kernel.org>,
Wei Yang <richard.weiyang@gmail.com>,
Yang Shi <shy828301@gmail.com>,
David Hildenbrand <david@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH v5 4/4] mm/shmem: fix shmem_swapin() race with swapoff
Date: Mon, 26 Apr 2021 00:53:34 -0600 [thread overview]
Message-ID: <CAOUHufZbT06isT_TU=x8d3P+AEHG8W=xd9GyX_5GHPNBT9KT9g@mail.gmail.com> (raw)
In-Reply-To: <20210425095419.3830298-5-linmiaohe@huawei.com>
On Sun, Apr 25, 2021 at 3:54 AM Miaohe Lin <linmiaohe@huawei.com> wrote:
>
> When I was investigating the swap code, I found the below possible race
> window:
>
> CPU 1 CPU 2
> ----- -----
> shmem_swapin
> swap_cluster_readahead
> if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) {
> swapoff
> ..
> si->swap_file = NULL;
> ..
> struct inode *inode = si->swap_file->f_mapping->host;[oops!]
>
> Close this race window by using get/put_swap_device() to guard against
> concurrent swapoff.
>
> Fixes: 8fd2e0b505d1 ("mm: swap: check if swap backing device is congested or not")
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> mm/shmem.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 26c76b13ad23..2dafd65b0b42 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1696,6 +1696,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> struct address_space *mapping = inode->i_mapping;
> struct shmem_inode_info *info = SHMEM_I(inode);
> struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm;
> + struct swap_info_struct *si;
> struct page *page;
> swp_entry_t swap;
> int error;
> @@ -1704,6 +1705,12 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> swap = radix_to_swp_entry(*pagep);
> *pagep = NULL;
>
> + /* Prevent swapoff from happening to us. */
> + si = get_swap_device(swap);
> + if (!si) {
> + error = EINVAL;
> + goto failed;
> + }
page is uninitialized?
> /* Look it up and read it in.. */
> page = lookup_swap_cache(swap, NULL, 0);
> if (!page) {
> @@ -1765,6 +1772,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> swap_free(swap);
>
> *pagep = page;
> + if (si)
> + put_swap_device(si);
> return 0;
> failed:
> if (!shmem_confirm_swap(mapping, index, swap))
> @@ -1775,6 +1784,9 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> put_page(page);
> }
>
> + if (si)
> + put_swap_device(si);
> +
> return error;
> }
>
> --
> 2.23.0
>
>
next prev parent reply other threads:[~2021-04-26 6:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-25 9:54 [PATCH v5 0/4] close various race windows for swap Miaohe Lin
2021-04-25 9:54 ` [PATCH v5 1/4] mm/swapfile: use percpu_ref to serialize against concurrent swapoff Miaohe Lin
2021-04-25 9:54 ` [PATCH v5 2/4] swap: fix do_swap_page() race with swapoff Miaohe Lin
2021-04-25 9:54 ` [PATCH v5 3/4] mm/swap: remove confusing checking for non_swap_entry() in swap_ra_info() Miaohe Lin
2021-04-25 9:54 ` [PATCH v5 4/4] mm/shmem: fix shmem_swapin() race with swapoff Miaohe Lin
2021-04-26 0:56 ` Huang, Ying
2021-04-26 6:53 ` Yu Zhao [this message]
2021-04-26 7:05 ` Miaohe Lin
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