[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 <rpeny...@suse.de>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Michal Hocko <mho...@suse.com>
Cc: Andrey Ryabinin <aryabi...@virtuozzo.com>
Cc: Joe Perches <j...@perches.com>
Cc: "Luis R. Rodriguez" <mcg...@kernel.org>
Cc: linux...@kvack.org
Cc: linux-kernel@vger.kernel.org
Cc: sta...@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