The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 19b482c29b6f3805f1d8e93015847b89e2f7f3b1 Mon Sep 17 00:00:00 2001 From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Date: Tue, 22 Mar 2022 14:42:05 -0700 Subject: [PATCH] mm: shmem: fix missing cache flush in shmem_mfill_atomic_pte() 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@xxxxxxxxxxxxx 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@xxxxxxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Fam Zheng <fam.zheng@xxxxxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Lars Persson <lars.persson@xxxxxxxx> Cc: Peter Xu <peterx@xxxxxxxxxx> Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> diff --git a/mm/shmem.c b/mm/shmem.c index f21eb0ef8ae0..01fd227b6947 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2364,8 +2364,10 @@ 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;
