linux-kernel - [PATCH AUTOSEL 05/14] mm: shmem: fix missing cache flush in shmem_mfill_atomic

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Date:   Thu, 28 Apr 2022 17:42:13 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Muchun Song <songmuchun@...edance.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Fam Zheng <fam.zheng@...edance.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Lars Persson <lars.persson@...s.com>,
        Peter Xu <peterx@...hat.com>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Zi Yan <ziy@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH AUTOSEL 05/14] mm: shmem: fix missing cache flush in shmem_mfill_atomic_pte()

From: Muchun Song <songmuchun@...edance.com>

commit 19b482c29b6f3805f1d8e93015847b89e2f7f3b1 upstream.

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.

Link: https://lkml.kernel.org/r/20220210123058.79206-6-songmuchun@bytedance.com
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@...edance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Axel Rasmussen <axelrasmussen@...gle.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Fam Zheng <fam.zheng@...edance.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Lars Persson <lars.persson@...s.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Xiongchun Duan <duanxiongchun@...edance.com>
Cc: Zi Yan <ziy@...dia.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/shmem.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index a09b29ec2b45..7a46419d331d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2357,8 +2357,10 @@ 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;
-- 
2.36.0