Re: [PATCH 1/2] mm/uffd: Fix pte marker when fork() without fork event

[Miaohe Lin]

On 2022/12/15 4:04, Peter Xu wrote:
> 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
> 
> Cc: <stable@xxxxxxxxxxxxxxx> # 5.19+
> Fixes: c56d1b62cce8 ("mm/shmem: handle uffd-wp during fork()")
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216808
> Reported-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>

Looks good to me. Thanks.
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>

Thanks,
Miaohe Lin