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Message-Id: <20170512111510.2697-1-mq@ucw.cz>
Date: Fri, 12 May 2017 13:15:10 +0200
From: Jan Moskyto Matejka <mq@....cz>
To: netdev@...r.kernel.org
Cc: Jan Moskyto Matejka <mq@....cz>, linux-kernel@...r.kernel.org,
David Ahern <dsa@...ulusnetworks.com>,
"David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
James Morris <jmorris@...ei.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Patrick McHardy <kaber@...sh.net>
Subject: [PATCH] net: ipv6: Truncate single route when it doesn't fit into dump buffer.
When rt6_fill_node() fails to fit the route into the buffer,
it drops the route, returns -EMSGSIZE and waits for buffer flush.
This condition is detected by non-null return value and non-empty
buffer; the buffer is flushed and rt6_fill_node() restarted.
However, when a single route generates such a long message that
it doesn't fit into the buffer itself, inet6_dump_fib() misinterprets
the non-null return value together with non-empty buffer as end of dump
and silently truncates the dump.
This patch fixes this by explicitly truncating the message and
inidicating it by NLM_F_TRUNC flag in its nlmsghdr.
Reproducer:
# ip -6 route show
... it shows some routes
# ip -6 route add fccc::/64 via fe80::ff:fe00:0 dev testdev table 2
# for a in $(seq 1 1000); do
ip -6 route append fccc::/64 via fe80::ff:fe00:$a dev testdev table 2
done
# ip -6 route show
... the output is truncated
This came to light by David Ahern's
commit beb1afac518dec5a15dc ("net: ipv6: Add support to dump multipath
routes via RTA_MULTIPATH attribute")
but obviously existed before, just hidden.
Signed-off-by: Jan Moskyto Matejka <mq@....cz>
---
include/net/ip6_route.h | 2 +-
include/uapi/linux/netlink.h | 1 +
net/ipv6/ip6_fib.c | 17 ++++++++++++++---
net/ipv6/route.c | 9 +++++++--
net/netlink/af_netlink.c | 7 ++++++-
5 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 9dc2c182a263..9b035b6bdf8c 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -156,7 +156,7 @@ struct rt6_rtnl_dump_arg {
struct net *net;
};
-int rt6_dump_route(struct rt6_info *rt, void *p_arg);
+int rt6_dump_route(struct rt6_info *rt, void *p_arg, int truncate);
void rt6_ifdown(struct net *net, struct net_device *dev);
void rt6_mtu_change(struct net_device *dev, unsigned int mtu);
void rt6_remove_prefsrc(struct inet6_ifaddr *ifp);
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index f3946a27bd07..1d463dbf89db 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -56,6 +56,7 @@ struct nlmsghdr {
#define NLM_F_ECHO 8 /* Echo this request */
#define NLM_F_DUMP_INTR 16 /* Dump was inconsistent due to sequence change */
#define NLM_F_DUMP_FILTERED 32 /* Dump was filtered as requested */
+#define NLM_F_TRUNC 64 /* Message truncated */
/* Modifiers to GET request */
#define NLM_F_ROOT 0x100 /* specify tree root */
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index d4bf2c68a545..4a962a61e559 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -310,13 +310,20 @@ static int fib6_dump_node(struct fib6_walker *w)
{
int res;
struct rt6_info *rt;
+ struct rt6_rtnl_dump_arg *arg = (struct rt6_rtnl_dump_arg *)w->args;
for (rt = w->leaf; rt; rt = rt->dst.rt6_next) {
- res = rt6_dump_route(rt, w->args);
+ res = rt6_dump_route(rt, w->args, 0);
+ if (res < 0 && arg->skb->len == 0)
+ /* One single route is too long for buffer.
+ * Will truncate it.
+ */
+ res = rt6_dump_route(rt, w->args, 1);
+
if (res < 0) {
/* Frame is full, suspend walking */
w->leaf = rt;
- return 1;
+ return res;
}
/* Multipath routes are dumped in one route with the
@@ -456,9 +463,14 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
cb->args[1] = e;
cb->args[0] = h;
- res = res < 0 ? res : skb->len;
if (res <= 0)
fib6_dump_end(cb);
+
+ if (res == -EMSGSIZE && skb->len)
+ res = skb->len;
+ else
+ res = res < 0 ? res : skb->len;
+
return res;
}
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index fb174b590fd3..0adcbdba87a1 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3539,11 +3539,16 @@ static int rt6_fill_node(struct net *net,
return 0;
nla_put_failure:
+ if (flags & NLM_F_TRUNC) {
+ nlmsg_end(skb, nlh);
+ return 0;
+ }
+
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}
-int rt6_dump_route(struct rt6_info *rt, void *p_arg)
+int rt6_dump_route(struct rt6_info *rt, void *p_arg, int truncate)
{
struct rt6_rtnl_dump_arg *arg = (struct rt6_rtnl_dump_arg *) p_arg;
struct net *net = arg->net;
@@ -3565,7 +3570,7 @@ int rt6_dump_route(struct rt6_info *rt, void *p_arg)
return rt6_fill_node(net,
arg->skb, rt, NULL, NULL, 0, RTM_NEWROUTE,
NETLINK_CB(arg->cb->skb).portid, arg->cb->nlh->nlmsg_seq,
- NLM_F_MULTI);
+ NLM_F_MULTI | (truncate ? NLM_F_TRUNC : 0));
}
static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 596eaff66649..f8102f976cad 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2177,7 +2177,12 @@ static int netlink_dump(struct sock *sk)
return 0;
}
- nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE, sizeof(len), NLM_F_MULTI);
+ if (len < 0)
+ nlh = nlmsg_put_answer(skb, cb, NLMSG_ERROR, sizeof(len), 0);
+ else
+ nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE, sizeof(len),
+ NLM_F_MULTI);
+
if (!nlh)
goto errout_skb;
--
2.11.0
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