This is a note to let you know that I've just added the patch titled mm/uffd: fix pte marker when fork() without fork event to the 6.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-uffd-fix-pte-marker-when-fork-without-fork-event.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 49d6d7fb631345b0f2957a7c4be24ad63903150f Mon Sep 17 00:00:00 2001 From: Peter Xu <peterx@xxxxxxxxxx> Date: Wed, 14 Dec 2022 15:04:52 -0500 Subject: mm/uffd: fix pte marker when fork() without fork event From: Peter Xu <peterx@xxxxxxxxxx> commit 49d6d7fb631345b0f2957a7c4be24ad63903150f upstream. Patch series "mm: Fixes on pte markers". Patch 1 resolves the syzkiller report from Pengfei. Patch 2 further harden pte markers when used with the recent swapin error markers. The major case is we should persist a swapin error marker after fork(), so child shouldn't read a corrupted page. This patch (of 2): When fork(), dst_vma is not guaranteed to have VM_UFFD_WP even if src may have it and has pte marker installed. The warning is improper along with the comment. The right thing is to inherit the pte marker when needed, or keep the dst pte empty. A vague guess is this happened by an accident when there's the prior patch to introduce src/dst vma into this helper during the uffd-wp feature got developed and I probably messed up in the rebase, since if we replace dst_vma with src_vma the warning & comment it all makes sense too. Hugetlb did exactly the right here (copy_hugetlb_page_range()). Fix the general path. Reproducer: https://github.com/xupengfe/syzkaller_logs/blob/main/221208_115556_copy_page_range/repro.c Bugzilla report: https://bugzilla.kernel.org/show_bug.cgi?id=216808 Link: https://lkml.kernel.org/r/20221214200453.1772655-1-peterx@xxxxxxxxxx Link: https://lkml.kernel.org/r/20221214200453.1772655-2-peterx@xxxxxxxxxx Fixes: c56d1b62cce8 ("mm/shmem: handle uffd-wp during fork()") Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> Reported-by: Pengfei Xu <pengfei.xu@xxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: Nadav Amit <nadav.amit@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> # 5.19+ Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/memory.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) --- a/mm/memory.c +++ b/mm/memory.c @@ -875,12 +875,8 @@ copy_nonpresent_pte(struct mm_struct *ds return -EBUSY; return -ENOENT; } else if (is_pte_marker_entry(entry)) { - /* - * We're copying the pgtable should only because dst_vma has - * uffd-wp enabled, do sanity check. - */ - WARN_ON_ONCE(!userfaultfd_wp(dst_vma)); - set_pte_at(dst_mm, addr, dst_pte, pte); + if (userfaultfd_wp(dst_vma)) + set_pte_at(dst_mm, addr, dst_pte, pte); return 0; } if (!userfaultfd_wp(dst_vma)) Patches currently in stable-queue which might be from peterx@xxxxxxxxxx are queue-6.1/migrate-hugetlb-check-for-hugetlb-shared-pmd-in-node-migration.patch queue-6.1/mm-uffd-fix-pte-marker-when-fork-without-fork-event.patch queue-6.1/selftests-vm-remove-__use_gnu-in-hugetlb-madvise.c.patch queue-6.1/mm-hugetlb-proc-check-for-hugetlb-shared-pmd-in-proc-pid-smaps.patch