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authorDavid S. Miller <davem@davemloft.net>2016-04-19 14:30:10 -0400
committerDavid S. Miller <davem@davemloft.net>2016-04-19 14:30:10 -0400
commit18402843bf88c2e9674e1a3a05c73b7d9b09ee05 (patch)
treeec57ed115507f9b2b6bf920575036d0ff5e656ec /net/core
parentb67d1df5ad0c227adc89d2913e933ed4addc5dab (diff)
net: Align IFLA_STATS64 attributes properly on architectures that need it.
Since the nlattr header is 4 bytes in size, it can cause the netlink attribute payload to not be 8-byte aligned. This is particularly troublesome for IFLA_STATS64 which contains 64-bit statistic values. Solve this by creating a dummy IFLA_PAD attribute which has a payload which is zero bytes in size. When HAVE_EFFICIENT_UNALIGNED_ACCESS is false, we insert an IFLA_PAD attribute into the netlink response when necessary such that the IFLA_STATS64 payload will be properly aligned. With help and suggestions from Eric Dumazet. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/rtnetlink.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a7a3d345134a..198ca2c99510 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -878,6 +878,9 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
+ nla_total_size(IFNAMSIZ) /* IFLA_QDISC */
+ nla_total_size(sizeof(struct rtnl_link_ifmap))
+ nla_total_size(sizeof(struct rtnl_link_stats))
+#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS
+ + nla_total_size(0) /* IFLA_PAD */
+#endif
+ nla_total_size(sizeof(struct rtnl_link_stats64))
+ nla_total_size(MAX_ADDR_LEN) /* IFLA_ADDRESS */
+ nla_total_size(MAX_ADDR_LEN) /* IFLA_BROADCAST */
@@ -1052,6 +1055,22 @@ static noinline_for_stack int rtnl_fill_stats(struct sk_buff *skb,
struct rtnl_link_stats64 *sp;
struct nlattr *attr;
+#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS
+ /* IF necessary, add a zero length NOP attribute so that the
+ * nla_data() of the IFLA_STATS64 will be 64-bit aligned.
+ *
+ * The nlattr header is 4 bytes in size, that's why we test
+ * if the skb->data _is_ aligned. This NOP attribute, plus
+ * nlattr header for IFLA_STATS64, will make nla_data() 8-byte
+ * aligned.
+ */
+ if (IS_ALIGNED((unsigned long)skb->data, 8)) {
+ attr = nla_reserve(skb, IFLA_PAD, 0);
+ if (!attr)
+ return -EMSGSIZE;
+ }
+#endif
+
attr = nla_reserve(skb, IFLA_STATS64,
sizeof(struct rtnl_link_stats64));
if (!attr)