xen-netback: validate queue numbers in xenvif_set_hash_mapping()

Checking them before the grant copy means nothing as to the validity of
the incoming request. As we shouldn't make the new data live before
having validated it, introduce a second instance of the mapping array.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 18 insertions, 8 deletions

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index a46a1e94505d..936c0b3e0ba2 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -241,8 +241,9 @@ struct xenvif_hash_cache {
 struct xenvif_hash {
         unsigned int alg;
         u32 flags;
+        bool mapping_sel;
         u8 key[XEN_NETBK_MAX_HASH_KEY_SIZE];
-        u32 mapping[XEN_NETBK_MAX_HASH_MAPPING_SIZE];
+        u32 mapping[2][XEN_NETBK_MAX_HASH_MAPPING_SIZE];
         unsigned int size;
         struct xenvif_hash_cache cache;
 };
diff --git a/drivers/net/xen-netback/hash.c b/drivers/net/xen-netback/hash.c
index 3b6fb5b3bdb2..dc9841ea2fff 100644
--- a/drivers/net/xen-netback/hash.c
+++ b/drivers/net/xen-netback/hash.c
@@ -324,7 +324,8 @@ u32 xenvif_set_hash_mapping_size(struct xenvif *vif, u32 size)
                 return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;
 
         vif->hash.size = size;
-        memset(vif->hash.mapping, 0, sizeof(u32) * size);
+        memset(vif->hash.mapping[vif->hash.mapping_sel], 0,
+               sizeof(u32) * size);
 
         return XEN_NETIF_CTRL_STATUS_SUCCESS;
 }
@@ -332,7 +333,7 @@ u32 xenvif_set_hash_mapping_size(struct xenvif *vif, u32 size)
 u32 xenvif_set_hash_mapping(struct xenvif *vif, u32 gref, u32 len,
                             u32 off)
 {
-        u32 *mapping = vif->hash.mapping;
+        u32 *mapping = vif->hash.mapping[!vif->hash.mapping_sel];
         struct gnttab_copy copy_op = {
                 .source.u.ref = gref,
                 .source.domid = vif->domid,
@@ -348,9 +349,8 @@ u32 xenvif_set_hash_mapping(struct xenvif *vif, u32 gref, u32 len,
         copy_op.dest.u.gmfn = virt_to_gfn(mapping + off);
         copy_op.dest.offset = xen_offset_in_page(mapping + off);
 
-        while (len-- != 0)
-                if (mapping[off++] >= vif->num_queues)
-                        return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;
+        memcpy(mapping, vif->hash.mapping[vif->hash.mapping_sel],
+               vif->hash.size * sizeof(*mapping));
 
         if (copy_op.len != 0) {
                 gnttab_batch_copy(&copy_op, 1);
@@ -359,6 +359,12 @@ u32 xenvif_set_hash_mapping(struct xenvif *vif, u32 gref, u32 len,
                         return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;
         }
 
+        while (len-- != 0)
+                if (mapping[off++] >= vif->num_queues)
+                        return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;
+
+        vif->hash.mapping_sel = !vif->hash.mapping_sel;
+
         return XEN_NETIF_CTRL_STATUS_SUCCESS;
 }
 
@@ -410,6 +416,8 @@ void xenvif_dump_hash_info(struct xenvif *vif, struct seq_file *m)
         }
 
         if (vif->hash.size != 0) {
+                const u32 *mapping = vif->hash.mapping[vif->hash.mapping_sel];
+
                 seq_puts(m, "\nHash Mapping:\n");
 
                 for (i = 0; i < vif->hash.size; ) {
@@ -422,7 +430,7 @@ void xenvif_dump_hash_info(struct xenvif *vif, struct seq_file *m)
                         seq_printf(m, "[%4u - %4u]: ", i, i + n - 1);
 
                         for (j = 0; j < n; j++, i++)
-                                seq_printf(m, "%4u ", vif->hash.mapping[i]);
+                                seq_printf(m, "%4u ", mapping[i]);
 
                         seq_puts(m, "\n");
                 }
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 92274c237200..f6ae23fc3f6b 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -162,7 +162,8 @@ static u16 xenvif_select_queue(struct net_device *dev, struct sk_buff *skb,
         if (size == 0)
                 return skb_get_hash_raw(skb) % dev->real_num_tx_queues;
 
-        return vif->hash.mapping[skb_get_hash_raw(skb) % size];
+        return vif->hash.mapping[vif->hash.mapping_sel]
+                                [skb_get_hash_raw(skb) % size];
 }
 
 static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)