vhost/vdpa: reject overflowing PA map page counts on 32-bit

vhost_vdpa_pa_map() adds the IOVA page offset to the user-controlled map
size before computing the number of pages to pin. On 32-bit systems,
where unsigned long is narrower than u64, that addition can overflow and
the code can pin and map fewer pages than the requested IOTLB range.

Reject sizes that overflow the unsigned long page-count calculation.

Fixes: 22af48cf91aa ("vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap()")
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Yousef Alhouseen <alhouseenyousef@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <CAMuQ4bX-iDvcUOPPY+NLz95tkRJYwWqvzAr=U48uNaub_HZLGw@mail.gmail.com>

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index ef642bc9f97e11f956c67590d8ff56adb22646e7..c3d913bd7cac7cd0deb050756f72b61629943f18 100644 (file)
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -1109,6 +1109,7 @@ static int vhost_vdpa_pa_map(struct vhost_vdpa *v,
        unsigned int gup_flags = FOLL_LONGTERM;
        unsigned long npages, cur_base, map_pfn, last_pfn = 0;
        unsigned long lock_limit, sz2pin, nchunks, i;
+       unsigned long page_offset;
        u64 start = iova;
        long pinned;
        int ret = 0;
@@ -1121,7 +1122,13 @@ static int vhost_vdpa_pa_map(struct vhost_vdpa *v,
        if (perm & VHOST_ACCESS_WO)
                gup_flags |= FOLL_WRITE;
 
-       npages = PFN_UP(size + (iova & ~PAGE_MASK));
+       page_offset = iova & ~PAGE_MASK;
+       if (size > ULONG_MAX - page_offset) {
+               ret = -EINVAL;
+               goto free;
+       }
+
+       npages = PFN_UP(size + page_offset);
        if (!npages) {
                ret = -EINVAL;
                goto free;