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

[ Upstream commit 46c22ffd2772201662350bc7b94b9ea9d3ee5ac2 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index aeb0a15bcbb7167bdf67c303534b3b5d1d752ee8..193205fb27774605c43146a22319f23479d5450e 100644 (file)
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -227,7 +227,7 @@ 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;
        /*