From: Mike Kravetz <mike.kravetz@oracle.com>
To: Muchun Song <songmuchun@bytedance.com>,
akpm@linux-foundation.org, zi.yan@cs.rutgers.edu,
kirill.shutemov@linux.intel.com, rientjes@google.com,
lars.persson@axis.com, ziy@nvidia.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
duanxiongchun@bytedance.com, fam.zheng@bytedance.com
Subject: Re: [PATCH v5 5/7] mm: shmem: fix missing cache flush in shmem_mfill_atomic_pte()
Date: Tue, 15 Feb 2022 11:11:51 -0800 [thread overview]
Message-ID: <39ab53c4-cb2f-82f4-1097-65d000284b23@oracle.com> (raw)
In-Reply-To: <20220210123058.79206-6-songmuchun@bytedance.com>
On 2/10/22 04:30, Muchun Song wrote:
> The userfaultfd calls shmem_mfill_atomic_pte() which does not do any
> cache flushing for the target page. Then the target page will be mapped
> to the user space with a different address (user address), which might
> have an alias issue with the kernel address used to copy the data from the
> user to. Insert flush_dcache_page() in non-zero-page case. And replace
> clear_highpage() with clear_user_highpage() which already considers
> the cache maintenance.
>
> Fixes: 8d1039634206 ("userfaultfd: shmem: add shmem_mfill_zeropage_pte for userfaultfd support")
> Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> mm/shmem.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
Thanks,
It might have been better to combine this and the next patch. When looking
at this, I noted the 'fallback to copy_from_user outside mmap_lock' case needs
to be addressed as well. It is in the next patch. No need to change.
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
--
Mike Kravetz
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index eb0fd9001130..2e17ec9231a2 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2371,8 +2371,10 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
> /* don't free the page */
> goto out_unacct_blocks;
> }
> +
> + flush_dcache_page(page);
> } else { /* ZEROPAGE */
> - clear_highpage(page);
> + clear_user_highpage(page, dst_addr);
> }
> } else {
> page = *pagep;
--
Mike Kravetz
next prev parent reply other threads:[~2022-02-15 19:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-10 12:30 [PATCH v5 0/7] Fix some cache flush bugs Muchun Song
2022-02-10 12:30 ` [PATCH v5 1/7] mm: thp: fix wrong cache flush in remove_migration_pmd() Muchun Song
2022-02-10 12:30 ` [PATCH v5 2/7] mm: fix missing cache flush for all tail pages of compound page Muchun Song
2022-02-10 12:30 ` [PATCH v5 3/7] mm: hugetlb: fix missing cache flush in copy_huge_page_from_user() Muchun Song
2022-02-10 12:30 ` [PATCH v5 4/7] mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte() Muchun Song
2022-02-10 12:30 ` [PATCH v5 5/7] mm: shmem: fix missing cache flush in shmem_mfill_atomic_pte() Muchun Song
2022-02-15 19:11 ` Mike Kravetz [this message]
2022-02-16 6:16 ` Muchun Song
2022-02-10 12:30 ` [PATCH v5 6/7] mm: userfaultfd: fix missing cache flush in mcopy_atomic_pte() and __mcopy_atomic() Muchun Song
2022-02-15 19:13 ` Mike Kravetz
2022-02-10 12:30 ` [PATCH v5 7/7] mm: replace multiple dcache flush with flush_dcache_folio() Muchun Song
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