diff options
| author | David S. Miller | 2016-04-19 14:30:10 -0400 |
|---|---|---|
| committer | David S. Miller | 2016-04-19 14:30:10 -0400 |
| commit | 18402843bf88c2e9674e1a3a05c73b7d9b09ee05 (patch) | |
| tree | ec57ed115507f9b2b6bf920575036d0ff5e656ec | |
| parent | b67d1df5ad0c227adc89d2913e933ed4addc5dab (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>
| -rw-r--r-- | include/uapi/linux/if_link.h | 1 | ||||
| -rw-r--r-- | net/core/rtnetlink.c | 19 |
2 files changed, 20 insertions, 0 deletions
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h index bb3a90b57199..5ffdcb34e35b 100644 --- a/include/uapi/linux/if_link.h +++ b/include/uapi/linux/if_link.h @@ -155,6 +155,7 @@ enum { IFLA_PROTO_DOWN, IFLA_GSO_MAX_SEGS, IFLA_GSO_MAX_SIZE, + IFLA_PAD, __IFLA_MAX }; 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) |