[PATCH 1/3] mm/vmalloc: fix size check for remap_vmalloc_range_partial()

[Roman Penyaev]

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
---
 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