Messages in this thread Patch in this message | | | From | Michael Riesch <> | Subject | [PATCH] rtnetlink: Call nlmsg_parse() with correct header length | Date | Mon, 8 Apr 2013 17:45:26 +0200 |
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Signed-off-by: Michael Riesch <michael.riesch@omicron.at> Cc: "David S. Miller" <davem@davemloft.net> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Benc <jbenc@redhat.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: linux-kernel@vger.kernel.org --- Habidere,
I encountered a netlink kernel warning when running avahi 0.6.31 on my system with kernel v3.4.35 (it appears several times):
netlink: 12 bytes leftover after parsing attributes.
Searching the web showed that commit "115c9b81928360d769a76c632bae62d15206a94a rtnetlink: Fix problem with buffer allocation" introduced this behaviour[1].
Now I - knowing nothing about netlink whatsoever - assume that the nlmsg_parse function is called with the wrong header length. In user space the request message consists out of the message header (struct nlmsghdr, 16 bytes) and an ifinfomsg (struct ifinfomsg, 16 bytes). After that, request attributes could follow. nlmsg_parse checks for this attributes after a given header length. In rtnl_get_link() this header length is sizeof(struct ifinfomsg), but in rtnl_calcit() as well as in rntl_dump_ifinfo() the header length is sizeof(struct rtgenmsg), which is 1 byte.
With this patch I got rid of these warnings. However, I do not know whether this is the correct solution, so I am looking forward to your comments. Regards, Michael
[1] http://lists.infradead.org/pipermail/libnl/2012-April/000515.html
net/core/rtnetlink.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 900fc61..ebf6ace 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -1065,7 +1065,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) rcu_read_lock(); cb->seq = net->dev_base_seq; - if (nlmsg_parse(cb->nlh, sizeof(struct rtgenmsg), tb, IFLA_MAX, + if (nlmsg_parse(cb->nlh, sizeof(struct ifinfomsg), tb, IFLA_MAX, ifla_policy) >= 0) { if (tb[IFLA_EXT_MASK]) @@ -1909,7 +1909,7 @@ static u16 rtnl_calcit(struct sk_buff *skb, struct nlmsghdr *nlh) u32 ext_filter_mask = 0; u16 min_ifinfo_dump_size = 0; - if (nlmsg_parse(nlh, sizeof(struct rtgenmsg), tb, IFLA_MAX, + if (nlmsg_parse(nlh, sizeof(struct ifinfomsg), tb, IFLA_MAX, ifla_policy) >= 0) { if (tb[IFLA_EXT_MASK]) ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]); -- 1.7.9.5
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