On 01.04.22 09:29, Miaohe Lin wrote:
> There is a bug in unuse_pte(): when swap page happens to be unreadable,
> page filled with random data is mapped into user address space. The fix
> is to check for PageUptodate and fail swapoff in case of error.
>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/swapfile.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 63c61f8b2611..e72a35de7a0f 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1795,6 +1795,10 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
> ret = 0;
> goto out;
> }
> + if (unlikely(!PageUptodate(page))) {
> + ret = -EIO;
> + goto out;
> + }
Yeah, we have the same handling in do_swap_page(), whereby we send a
SIGBUS because we're dealing with an actual access.
Interestingly, folio_test_uptodate() states:
"Anonymous and CoW folios are always uptodate."
@Willy, is that true or is the swapin case not documented there?
--
Thanks,
David / dhildenb
