s390/uv: fully validate the VMA before calling follow_page()

We should not walk/touch page tables outside of VMA boundaries when
holding only the mmap sem in read mode. Evil user space can modify the
VMA layout just before this function runs and e.g., trigger races with
page table removal code since commit dd2283f2605e ("mm: mmap: zap pages
with read mmap_sem in munmap").

find_vma() does not check if the address is >= the VMA start address;
use vma_lookup() instead.

Fixes: 214d9bbcd3a6 ("s390/mm: provide memory management functions for protected KVM guests")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Link: https://lore.kernel.org/r/20210909162248.14969-6-david@redhat.com
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 5a656c7b7a67aee4750be534dfd941cb49983ed0..f95ccbd39692581a06842dc29e812d2c37ae280c 100644 (file)
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -212,7 +212,7 @@ again:
        uaddr = __gmap_translate(gmap, gaddr);
        if (IS_ERR_VALUE(uaddr))
                goto out;
-       vma = find_vma(gmap->mm, uaddr);
+       vma = vma_lookup(gmap->mm, uaddr);
        if (!vma)
                goto out;
        /*