xen/pvcalls: fix unsigned less than zero error check

The check on bedata->ref is never true because ref is an unsigned
integer. Fix this by assigning signed int ret to the return of the
call to gnttab_claim_grant_reference so the -ve return can be checked.

Detected by CoverityScan, CID#1460358 ("Unsigned compared against 0")

Fixes: 219681909913 ("xen/pvcalls: connect to the backend")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index ed94ea0b4b8e7db8ae8a8063f9886318eebbc2c6..60a0ad81d4cf2ecc704091c119bb11eae98330b7 100644 (file)
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -1186,11 +1186,10 @@ static int pvcalls_front_probe(struct xenbus_device *dev,
        ret = gnttab_alloc_grant_references(1, &gref_head);
        if (ret < 0)
                goto error;
-       bedata->ref = gnttab_claim_grant_reference(&gref_head);
-       if (bedata->ref < 0) {
-               ret = bedata->ref;
+       ret = gnttab_claim_grant_reference(&gref_head);
+       if (ret < 0)
                goto error;
-       }
+       bedata->ref = ret;
        gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
                                        virt_to_gfn((void *)sring), 0);