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.
Can this actually happen? I am not really familiar with all the callers of this API but VM_NO_GUARD is not really used wildly in the kernel. All I can see is kasan na arm64 which doesn't really seem to use it for vmalloc.
So is the problem real or this is a mere cleanup?
Signed-off-by: Roman Penyaev rpenyaev@suse.de Cc: Andrew Morton akpm@linux-foundation.org Cc: Michal Hocko mhocko@suse.com Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Joe Perches joe@perches.com Cc: "Luis R. Rodriguez" mcgrof@kernel.org Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org
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