On Thu, Jul 4, 2024 at 11:27 AM Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> wrote:
>
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
>
> mmap_region is already passed sanitized addr and len, so change the
> call to do_vmi_munmap() to do_vmi_align_munmap() and inline the other
> checks.
Hmm. I think such refactoring when you want to skip some checks would
be done a bit differently... You would introduce a __do_vmi_munmap()
function which is called at the end of do_vmi_munmap() after the
checks and then call __do_vmi_munmap() directly wherever you want to
skip the checks. That would avoid code duplication. Any reason that
can't be done here?
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> mm/mmap.c | 20 ++++++++++++++------
> 1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 8d9be791997a..e9858ca8bbd4 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2937,12 +2937,20 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> return -ENOMEM;
> }
>
> - /* Unmap any existing mapping in the area */
> - error = do_vmi_munmap(&vmi, mm, addr, len, uf, false);
> - if (error == -EPERM)
> - return error;
> - else if (error)
> - return -ENOMEM;
> +
> + if (unlikely(!can_modify_mm(mm, addr, end)))
> + return -EPERM;
> +
> + /* arch_unmap() might do unmaps itself. */
> + arch_unmap(mm, addr, end);
> +
> + /* Find the first overlapping VMA */
> + vma = vma_find(&vmi, end);
> + if (vma) {
> + if (do_vmi_align_munmap(&vmi, vma, mm, addr, end, uf, false))
> + return -ENOMEM;
> + vma = NULL;
> + }
>
> /*
> * Private writable mapping: check memory availability
> --
> 2.43.0
>
