xen/xenbus: ensure xenbus_map_ring_valloc() returns proper grant status
[ Upstream commit 6b51fd3f65a22e3d1471b18a1d56247e246edd46 ]
xenbus_map_ring_valloc() maps a ring page and returns the status of the
used grant (0 meaning success).
There are Xen hypervisors which might return the value 1 for the status
of a failed grant mapping due to a bug. Some callers of
xenbus_map_ring_valloc() test for errors by testing the returned status
to be less than zero, resulting in no error detected and crashing later
due to a not available ring page.
Set the return value of xenbus_map_ring_valloc() to GNTST_general_error
in case the grant status reported by Xen is greater than zero.
This is part of XSA-316.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wl@xen.org>
Link: https://lore.kernel.org/r/20200326080358.1018-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 056da6e..df27cef 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -469,7 +469,14 @@
int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
unsigned int nr_grefs, void **vaddr)
{
- return ring_ops->map(dev, gnt_refs, nr_grefs, vaddr);
+ int err;
+
+ err = ring_ops->map(dev, gnt_refs, nr_grefs, vaddr);
+ /* Some hypervisors are buggy and can return 1. */
+ if (err > 0)
+ err = GNTST_general_error;
+
+ return err;
}
EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);