[Xen-devel] [PATCH 21/25] argo: add array_index_nospec to guard the result of the hash func

[Christopher Clark <christopher.w.clark@xxxxxxxxx>]

This is out of an abundance of caution, since this is a very basic hash
function, chosen more for its bucket distribution properties to cluster related
rings rather than for cryptographic strength or any uniformness of output,
and it operates upon values supplied by the guest just before being used as an
array index.

Signed-off-by: Christopher Clark <christopher.clark6@xxxxxxxxxxxxxx>
---
 xen/common/argo.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/common/argo.c b/xen/common/argo.c
index 39778fd..fa969ab 100644
--- a/xen/common/argo.c
+++ b/xen/common/argo.c
@@ -23,6 +23,7 @@
 #include <xen/event.h>
 #include <xen/domain_page.h>
 #include <xen/guest_access.h>
+#include <xen/nospec.h>
 #include <xen/time.h>
 #include <xsm/xsm.h>
 
@@ -1094,7 +1095,7 @@ argo_ring_find_info(const struct domain *d, const struct 
argo_ring_id *id)
 
     ASSERT(rw_is_locked(&d->argo->lock));
 
-    hash = argo_hash_fn(id);
+    hash = array_index_nospec(argo_hash_fn(id), ARGO_HTABLE_SIZE);
 
     argo_dprintk("d->argo=%p, d->argo->ring_hash[%d]=%p id=%p\n",
                  d->argo, hash, d->argo->ring_hash[hash].first, id);
@@ -1349,7 +1350,8 @@ argo_register_ring(struct domain *d,
                 ring_info->id = ring.id;
                 INIT_HLIST_HEAD(&ring_info->pending);
 
-                hash = argo_hash_fn(&ring_info->id);
+                hash = array_index_nospec(argo_hash_fn(&ring_info->id),
+                                          ARGO_HTABLE_SIZE);
                 hlist_add_head(&ring_info->node, &d->argo->ring_hash[hash]);
 
                 printk(XENLOG_INFO "argo: vm%u registering ring (vm%u:%x 
vm%d)\n",
-- 
2.1.4


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