On 01.04.22 10:10, Miaohe Lin wrote:
> When old_len == new_len, do_munmap will return -EINVAL due to len == 0.
> This errno will be simply ignored because of old_len != new_len check.
> So it is unnecessary to call do_munmap when old_len == new_len because
> nothing is actually done.
>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/mremap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mremap.c b/mm/mremap.c
> index e776d4c2345c..dd966621a056 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -817,9 +817,9 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
> goto out;
> }
>
> - if (old_len >= new_len) {
> + if (old_len > new_len) {
> ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
> - if (ret && old_len != new_len)
> + if (ret)
> goto out;
> old_len = new_len;
> }
I remember stumbling over that myself a year ago or so but dig not
deeper. But indeed, both variants (mmu, nommu) return -EINVAL in case
len (old_len - new_len) == 0.
Maybe that used to be different before ecc1a8993751 ("do_mremap()
untangling, part 2"), but it doesn't look like it.
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
