On Thu 03-01-19 15:59:52, Roman Penyaev wrote:
> area->size can include adjacent guard page but get_vm_area_size()
> returns actual size of the area.
>
> This fixes possible kernel crash when userspace tries to map area
> on 1 page bigger: size check passes but the following vmalloc_to_page()
> returns NULL on last guard (non-existing) page.
>
> Signed-off-by: Roman Penyaev <rpenyaev@xxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> Cc: Joe Perches <joe@xxxxxxxxxxx>
> Cc: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
Forgot to add
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Although I am not really sure the stable backport is really needed as I
haven't seen any explicit example of a buggy kernel code to trigger the
issue.
> ---
> mm/vmalloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 871e41c55e23..2cd24186ba84 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2248,7 +2248,7 @@ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
> if (!(area->flags & VM_USERMAP))
> return -EINVAL;
>
> - if (kaddr + size > area->addr + area->size)
> + if (kaddr + size > area->addr + get_vm_area_size(area))
> return -EINVAL;
>
> do {
> --
> 2.19.1
--
Michal Hocko
SUSE Labs
