[Xen-devel] [PATCH 2/3] xen-netback: validate queue numbers in xenvif_set_hash_mapping()

["Jan Beulich" <JBeulich@xxxxxxxx>]

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@xxxxxxxx>

---
 drivers/net/xen-netback/common.h    |    3 ++-
 drivers/net/xen-netback/hash.c      |   20 ++++++++++++++------
 drivers/net/xen-netback/interface.c |    3 ++-
 3 files changed, 18 insertions(+), 8 deletions(-)

--- 4.19-rc1-xen-netback-set-hash-mapping.orig/drivers/net/xen-netback/common.h
+++ 4.19-rc1-xen-netback-set-hash-mapping/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;
 };
--- 4.19-rc1-xen-netback-set-hash-mapping.orig/drivers/net/xen-netback/hash.c
+++ 4.19-rc1-xen-netback-set-hash-mapping/drivers/net/xen-netback/hash.c
@@ -324,7 +324,8 @@ u32 xenvif_set_hash_mapping_size(struct
                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
 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 xenvi
        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 xenvi
                        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
        }
 
        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
                        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");
                }
--- 
4.19-rc1-xen-netback-set-hash-mapping.orig/drivers/net/xen-netback/interface.c
+++ 4.19-rc1-xen-netback-set-hash-mapping/drivers/net/xen-netback/interface.c
@@ -162,7 +162,8 @@ static u16 xenvif_select_queue(struct ne
        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)





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