[PATCH] xen/xenbus: fix xenbus_setup_ring()

[Juergen Gross <jgross@xxxxxxxx>]

Commit 4573240f0764 ("xen/xenbus: eliminate xenbus_grant_ring()")
introduced an error for initialization of multi-page rings.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 4573240f0764 ("xen/xenbus: eliminate xenbus_grant_ring()")
Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 drivers/xen/xenbus/xenbus_client.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_client.c 
b/drivers/xen/xenbus/xenbus_client.c
index d5f3f763717e..caa5c5c32f8e 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -382,9 +382,10 @@ int xenbus_setup_ring(struct xenbus_device *dev, gfp_t 
gfp, void **vaddr,
        unsigned long ring_size = nr_pages * XEN_PAGE_SIZE;
        grant_ref_t gref_head;
        unsigned int i;
+       void *addr;
        int ret;
 
-       *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO);
+       addr = *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO);
        if (!*vaddr) {
                ret = -ENOMEM;
                goto err;
@@ -401,13 +402,15 @@ int xenbus_setup_ring(struct xenbus_device *dev, gfp_t 
gfp, void **vaddr,
                unsigned long gfn;
 
                if (is_vmalloc_addr(*vaddr))
-                       gfn = pfn_to_gfn(vmalloc_to_pfn(vaddr[i]));
+                       gfn = pfn_to_gfn(vmalloc_to_pfn(addr));
                else
-                       gfn = virt_to_gfn(vaddr[i]);
+                       gfn = virt_to_gfn(addr);
 
                grefs[i] = gnttab_claim_grant_reference(&gref_head);
                gnttab_grant_foreign_access_ref(grefs[i], dev->otherend_id,
                                                gfn, 0);
+
+               addr += PAGE_SIZE;
        }
 
        return 0;
-- 
2.35.3