From: Sowmini Varadhan <sowmini.varadhan@oracle•com>
To: netdev@vger•kernel.org
Subject: [RFC] Kernel unaligned access at __skb_flow_dissect
Date: Fri, 29 Jan 2016 13:06:51 -0500 [thread overview]
Message-ID: <20160129180651.GA17127@oracle.com> (raw)
There is an unaligned access at __skb_flow_dissect when it calls
ip6_flowlabel() with the call stack
__skb_flow_dissect+0x2a8/0x87c
eth_get_headlen+0x5c/0xaxa4
ixgbe_clean_rx_irq+0x5cc/0xb20 [ixgbe]
ixgbe_poll+0x5a4/0x760 [ixgbe]
net_rx_action+0x13c/0x354
:
Essentially, ixgbe_pull_tail() is trying to figure out how much
to pull, in order to have an aligned buffer:
pull_len = eth_get_headlen(va, IXGBE_RX_HDR_SIZE);
/* align pull length to size of long to optimize memcpy performance */
skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long)));
and seems like the unaligned access is unavoidable here (see comments
in __skb_get_poff, for example).
This (below) is what I came up with, to get rid of the unaligned access
errors on sparc, Is there a better solution? (Not having access
to struct ip6_hdr in this file made put_unaligned usage non-obvious)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -102,6 +102,17 @@ __be32 __skb_flow_get_ports(const struct sk_buff *skb, int
}
EXPORT_SYMBOL(__skb_flow_get_ports);
+static inline __be32 ip6_flowlabel_align(const u8 *hdr)
+{
+ union {
+ __u8 w[4];
+ __u32 flow;
+ } ip6_flow;
+
+ memcpy(ip6_flow.w, hdr, 4);
+ return (ip6_flow.flow & IPV6_FLOWLABEL_MASK);
+}
+
/**
* __skb_flow_dissect - extract the flow_keys struct and return it
* @skb: sk_buff to extract the flow from, can be NULL if the rest are specifie
@@ -230,7 +241,7 @@ ipv6:
key_control->addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
}
- flow_label = ip6_flowlabel(iph);
+ flow_label = ip6_flowlabel_align((const u8 *)iph);
if (flow_label) {
if (dissector_uses_key(flow_dissector,
FLOW_DISSECTOR_KEY_FLOW_LABEL)) {
next reply other threads:[~2016-01-29 18:07 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 18:06 Sowmini Varadhan [this message]
2016-01-29 18:33 ` [RFC] Kernel unaligned access at __skb_flow_dissect Eric Dumazet
2016-01-29 18:40 ` Eric Dumazet
2016-01-29 19:08 ` David Miller
2016-01-29 19:39 ` Eric Dumazet
2016-01-29 18:54 ` Eric Dumazet
2016-01-29 19:22 ` Sowmini Varadhan
2016-01-29 21:00 ` Tom Herbert
2016-01-29 21:09 ` Sowmini Varadhan
2016-01-29 21:33 ` Tom Herbert
2016-01-29 23:00 ` Tom Herbert
2016-01-29 23:04 ` Sowmini Varadhan
2016-01-29 23:31 ` Tom Herbert
2016-01-29 23:58 ` Sowmini Varadhan
2016-01-30 0:47 ` Tom Herbert
2016-01-30 1:18 ` David Miller
2016-01-30 2:15 ` Eric Dumazet
2016-01-31 22:13 ` Tom Herbert
2016-02-01 0:04 ` Eric Dumazet
2016-01-29 19:06 ` David Miller
2016-01-29 19:37 ` Eric Dumazet
2016-01-29 19:41 ` David Miller
2016-01-29 19:44 ` Sowmini Varadhan
2016-01-29 20:01 ` Eric Dumazet
2016-01-29 20:06 ` Eric Dumazet
2016-01-29 21:16 ` Alexander Duyck
2016-01-29 21:33 ` Eric Dumazet
2016-01-29 22:08 ` Alexander Duyck
2016-01-29 22:28 ` Eric Dumazet
2016-01-29 23:00 ` Alexander Duyck
2016-02-01 16:55 ` David Laight
2016-02-01 17:25 ` Eric Dumazet
2016-01-29 19:04 ` David Miller
2016-01-30 2:49 ` [net PATCH] flow_dissector: Fix unaligned access in __skb_flow_dissector when used by eth_get_headlen Alexander Duyck
2016-01-30 3:23 ` Eric Dumazet
2016-01-30 3:35 ` David Miller
2016-01-30 4:46 ` Alexander Duyck
2016-01-30 16:17 ` Sowmini Varadhan
2016-01-30 17:43 ` Tom Herbert
2016-01-30 19:12 ` Sowmini Varadhan
2016-01-30 18:36 ` Alexander Duyck
2016-01-30 19:26 ` Eric Dumazet
2016-01-31 1:13 ` Alexander Duyck
2016-01-31 3:45 ` David Miller
2016-01-31 9:12 ` Alexander Duyck
2016-01-31 19:17 ` David Miller
2016-01-31 21:23 ` Sowmini Varadhan
2016-02-01 16:50 ` David Laight
2016-02-01 18:18 ` Alexander Duyck
2016-02-02 9:47 ` David Laight
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