"ip route get $daddr iif eth0 from $saddr" causes:
 BUG: KASAN: use-after-free in ip_route_input_rcu+0x1535/0x1b50
 Call Trace:
  ip_route_input_rcu+0x1535/0x1b50
  ip_route_input_noref+0xf9/0x190
  tcp_v4_early_demux+0x1a4/0x2b0
  ip_rcv+0xbcb/0xc05
  __netif_receive_skb+0x9c/0xd0
  netif_receive_skb_internal+0x5a8/0x890

Problem is that inet_rtm_getroute calls either ip_route_input_rcu (if an
iif was provided) or ip_route_output_key_hash_rcu.

But ip_route_input_rcu, unlike ip_route_output_key_hash_rcu, already
associates the dst_entry with the skb.  This clears the SKB_DST_NOREF
bit (i.e. skb_dst_drop will release/free the entry while it should not).

Thus only set the dst if we called ip_route_output_key_hash_rcu().

I tested this patch by running:
 while true;do ip r get 10.0.1.2;done > /dev/null &
 while true;do ip r get 10.0.1.2 iif eth0  from 10.0.1.1;done > /dev/null &
... and saw no crash or memory leak.

Cc: Roopa Prabhu <roopa@cumulusnetworks.com>
Cc: David Ahern <dsahern@gmail.com>
Fixes: ba52d61e ("ipv4: route: restore skb_dst_set in inet_rtm_getroute")
Signed-off-by: NFlorian Westphal <fw@strlen.de>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Using get_random_int here is faster, more fitting of the use case, and
just as cryptographically secure. It also has the benefit of providing
better randomness at early boot, which is when many of these structures
are assigned.

Also, semantically, it's not really proper to have been assigning an
atomic_t in this way before, even if in practice it works fine.
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

DST_NOCACHE flag check has been removed from dst_release() and
dst_hold_safe() in a previous patch because all the dst are now ref
counted properly and can be released based on refcnt only.
Looking at the rest of the DST_NOCACHE use, all of them can now be
removed or replaced with other checks.
So this patch gets rid of all the DST_NOCACHE usage and remove this flag
completely.
Signed-off-by: NWei Wang <weiwan@google.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Now that all the components have been changed to release dst based on
refcnt only and not depend on dst gc anymore, we can remove the
temporary flag DST_NOGC.

Note that we also need to remove the DST_NOCACHE check in dst_release()
and dst_hold_safe() because now all the dst are released based on refcnt
and behaves as DST_NOCACHE.
Signed-off-by: NWei Wang <weiwan@google.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

With the previous preparation patches, we are ready to get rid of the
dst gc operation in ipv4 code and release dst based on refcnt only.
So this patch adds DST_NOGC flag for all IPv4 dst and remove the calls
to dst_free().
At this point, all dst created in ipv4 code do not use the dst gc
anymore and will be destroyed at the point when refcnt drops to 0.
Signed-off-by: NWei Wang <weiwan@google.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch checks all the calls to
dst_hold()/skb_dst_force()/dst_clone()/dst_use() to see if
dst_hold_safe() is needed to avoid double free issue if dst
gc is removed and dst_release() directly destroys dst when
dst->__refcnt drops to 0.

In tx path, TCP hold sk->sk_rx_dst ref count and also hold sock_lock().
UDP and other similar protocols always hold refcount for
skb->_skb_refdst. So both paths seem to be safe.

In rx path, as it is lockless and skb_dst_set_noref() is likely to be
used, dst_hold_safe() should always be used when trying to hold dst.

In the routing code, if dst is held during an rcu protected session, it
is necessary to call dst_hold_safe() as the current dst might be in its
rcu grace period.
Signed-off-by: NWei Wang <weiwan@google.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

As the intend of this patch series is to completely remove dst gc,
we need to call dst_dev_put() to release the reference to dst->dev
when removing routes from fib because we won't keep the gc list anymore
and will lose the dst pointer right after removing the routes.
Without the gc list, there is no way to find all the dst's that have
dst->dev pointing to the going-down dev.
Hence, we are doing dst_dev_put() immediately before we lose the last
reference of the dst from the routing code. The next dst_check() will
trigger a route re-lookup to find another route (if there is any).
Signed-off-by: NWei Wang <weiwan@google.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In IPv4 routing code, fib_nh and fib_nh_exception can hold pointers
to struct rtable but they never increment dst->__refcnt.
This leads to the need of the dst garbage collector because when user
is done with this dst and calls dst_release(), it can only decrement
dst->__refcnt and can not free the dst even it sees dst->__refcnt
drops from 1 to 0 (unless DST_NOCACHE flag is set) because the routing
code might still hold reference to it.
And when the routing code tries to delete a route, it has to put the
dst to the gc_list if dst->__refcnt is not yet 0 and have a gc thread
running periodically to check on dst->__refcnt and finally to free dst
when refcnt becomes 0.

This patch increments dst->__refcnt when
fib_nh/fib_nh_exception holds reference to this dst and properly release
the dst when fib_nh/fib_nh_exception has been updated with a new dst.

This patch is a preparation in order to fully get rid of dst gc later.
Signed-off-by: NWei Wang <weiwan@google.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Existing ipv4/6_blackhole_route() code generates a blackhole route
with dst->dev pointing to the passed in dst->dev.
It is not necessary to hold reference to the passed in dst->dev
because the packets going through this route are dropped anyway.
A loopback interface is good enough so that we don't need to worry about
releasing this dst->dev when this dev is going down.
Signed-off-by: NWei Wang <weiwan@google.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

recent updates to inet_rtm_getroute dropped skb_dst_set in
inet_rtm_getroute. This patch restores it because it is
needed to release the dst correctly.

Fixes: 3765d35e ("net: ipv4: Convert inet_rtm_getroute to rcu versions of route lookup")
Reported-by: NJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Andrey Konovalov reported crashes in ipv4_mtu()

I could reproduce the issue with KASAN kernels, between
10.246.7.151 and 10.246.7.152 :

1) 20 concurrent netperf -t TCP_RR -H 10.246.7.152 -l 1000 &

2) At the same time run following loop :
while :
do
 ip ro add 10.246.7.152 dev eth0 src 10.246.7.151 mtu 1500
 ip ro del 10.246.7.152 dev eth0 src 10.246.7.151 mtu 1500
done

Cong Wang attempted to add back rt->fi in commit
82486aa6 ("ipv4: restore rt->fi for reference counting")
but this proved to add some issues that were complex to solve.

Instead, I suggested to add a refcount to the metrics themselves,
being a standalone object (in particular, no reference to other objects)

I tried to make this patch as small as possible to ease its backport,
instead of being super clean. Note that we believe that only ipv4 dst
need to take care of the metric refcount. But if this is wrong,
this patch adds the basic infrastructure to extend this to other
families.

Many thanks to Julian Anastasov for reviewing this patch, and Cong Wang
for his efforts on this problem.

Fixes: 2860583f ("ipv4: Kill rt->fi")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reported-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NJulian Anastasov <ja@ssi.bg>
Acked-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch adds support to return matched fib result when RTM_F_FIB_MATCH
flag is specified in RTM_GETROUTE request. This is useful for user-space
applications/controllers wanting to query a matching route.
Signed-off-by: NRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Convert inet_rtm_getroute to use ip_route_input_rcu and
ip_route_output_key_hash_rcu passing the fib_result arg to both.
The rcu lock is held through the creation of the response, so the
rtable/dst does not need to be attached to the skb and is passed
to rt_fill_info directly.

In converting from ip_route_output_key to ip_route_output_key_hash_rcu
the xfrm_lookup_route in ip_route_output_flow is dropped since
flowi4_proto is not set for a route get request.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

rt_fill_info has 1 caller with the event set to RTM_NEWROUTE. Given that
remove the arg and use RTM_NEWROUTE directly in rt_fill_info.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

A later patch wants access to the fib result on an input route lookup
with the rcu lock held. Refactor ip_route_input_noref pushing the logic
between rcu_read_lock ... rcu_read_unlock into a new helper that takes
the fib_result as an input arg.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

A later patch wants access to the fib result on an output route lookup
with the rcu lock held. Refactor __ip_route_output_key_hash, pushing
the logic between rcu_read_lock ... rcu_read_unlock into a new helper
with the fib_result as an input arg.

To keep the name length under control remove the leading underscores
from the name and add _rcu to the name of the new helper indicating it
is called with the rcu read lock held.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This reverts commit 82486aa6.

As implemented, this causes dangling netdevice refs.
Reported-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

IPv4 dst could use fi->fib_metrics to store metrics but fib_info
itself is refcnt'ed, so without taking a refcnt fi and
fi->fib_metrics could be freed while dst metrics still points to
it. This triggers use-after-free as reported by Andrey twice.

This patch reverts commit 2860583f ("ipv4: Kill rt->fi") to
restore this reference counting. It is a quick fix for -net and
-stable, for -net-next, as Eric suggested, we can consider doing
reference counting for metrics itself instead of relying on fib_info.

IPv6 is very different, it copies or steals the metrics from mx6_config
in fib6_commit_metrics() so probably doesn't need a refcnt.

Decnet has already done the refcnt'ing, see dn_fib_semantic_match().

Fixes: 2860583f ("ipv4: Kill rt->fi")
Reported-by: NAndrey Konovalov <andreyknvl@google.com>
Tested-by: NAndrey Konovalov <andreyknvl@google.com>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

David reported that doing the following:

    ip li add red type vrf table 10
    ip link set dev eth1 vrf red
    ip addr add 127.0.0.1/8 dev red
    ip link set dev eth1 up
    ip li set red up
    ping -c1 -w1 -I red 127.0.0.1
    ip li del red

when either policy routing IP rules are present or the local table
lookup ip rule is before the l3mdev lookup results in a hang with
these messages:

    unregister_netdevice: waiting for red to become free. Usage count = 1

The problem is caused by caching the dst used for sending the packet
out of the specified interface on a local route with a different
nexthop interface. Thus the dst could stay around until the route in
the table the lookup was done is deleted which may be never.

Address the problem by not forcing output device to be the l3mdev in
the flow's output interface if the lookup didn't use the l3mdev. This
then results in the dst using the right device according to the route.

Changes in v2:
 - make the dev_out passed in by __ip_route_output_key_hash correct
   instead of checking the nh dev if FLOWI_FLAG_SKIP_NH_OIF is set as
   suggested by David.

Fixes: 5f02ce24 ("net: l3mdev: Allow the l3mdev to be a loopback")
Reported-by: NDavid Ahern <dsa@cumulusnetworks.com>
Suggested-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NRobert Shearman <rshearma@brocade.com>
Acked-by: NDavid Ahern <dsa@cumulusnetworks.com>
Tested-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add netlink_ext_ack arg to rtnl_doit_func. Pass extack arg to nlmsg_parse
for doit functions that call it directly.

This is the first step to using extended error reporting in rtnetlink.
>From here individual subsystems can be updated to set netlink_ext_ack as
needed.
Signed-off-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Pass the new extended ACK reporting struct to all of the generic
netlink parsing functions. For now, pass NULL in almost all callers
(except for some in the core.)
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

1. Don't get the metric RTAX_ADVMSS of dst.
There are two reasons.
1) Its caller dst_metric_advmss has already invoke dst_metric_advmss
before invoke default_advmss.
2) The ipv4_default_advmss is used to get the default mss, it should
not try to get the metric like ip6_default_advmss.

2. Use sizeof(tcphdr)+sizeof(iphdr) instead of literal 40.

3. Define one new macro IPV4_MAX_PMTU instead of 65535 according to
RFC 2675, section 5.1.
Signed-off-by: NGao Feng <fgao@ikuai8.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

inet_rtm_getroute synthesizes a skeletal ICMP skb, which is passed to
ip_route_input when iif is given. If a multipath route is present for
the designated destination, fib_multipath_hash ends up being called with
that skb. However, as that skb contains no information beyond the
protocol type, the calculated hash does not match the one we would see
for a real packet.

There is currently no way to fix this for layer 4 hashing, as
RTM_GETROUTE doesn't have the necessary information to create layer 4
headers. To fix this for layer 3 hashing, set appropriate saddr/daddrs
in the skb and also change the protocol to UDP to avoid special
treatment for ICMP.
Signed-off-by: NFlorian Larysch <fl@n621.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

inet_rtm_getroute synthesizes a skeletal ICMP skb, which is passed to
ip_route_input when iif is given. If a multipath route is present for
the designated destination, ip_multipath_icmp_hash ends up being called,
which uses the source/destination addresses within the skb to calculate
a hash. However, those are not set in the synthetic skb, causing it to
return an arbitrary and incorrect result.

Instead, use UDP, which gets no such special treatment.
Signed-off-by: NFlorian Larysch <fl@n621.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch adds support for ECMP hash policy choice via a new sysctl
called fib_multipath_hash_policy and also adds support for L4 hashes.
The current values for fib_multipath_hash_policy are:
 0 - layer 3 (default)
 1 - layer 4
If there's an skb hash already set and it matches the chosen policy then it
will be used instead of being calculated (currently only for L4).
In L3 mode we always calculate the hash due to the ICMP error special
case, the flow dissector's field consistentification should handle the
address order thus we can remove the address reversals.
If the skb is provided we always use it for the hash calculation,
otherwise we fallback to fl4, that is if skb is NULL fl4 has to be set.
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Restore the lost masking of TOS in input route code to
allow ip rules to match it properly.

Problem [1] noticed by Shmulik Ladkani <shmulik.ladkani@gmail.com>

[1] http://marc.info/?t=137331755300040&r=1&w=2

Fixes: 89aef892 ("ipv4: Delete routing cache.")
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Avoid matching of random stack value for uid when rules
are looked up on input route or when RP filter is used.
Problem should affect only setups that use ip rules with
uid range.

Fixes: 622ec2c9 ("net: core: add UID to flows, rules, and routes")
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add confirm_neigh method to dst_ops and use it from IPv4 and IPv6
to lookup and confirm the neighbour. Its usage via the new helper
dst_confirm_neigh() should be restricted to MSG_PROBE users for
performance reasons.

For XFRM prefer the last tunnel address, if present. With help
from Steffen Klassert.
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Acked-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

rtm_table is an 8-bit field while table ids are allowed up to u32. Commit
709772e6 ("net: Fix routing tables with id > 255 for legacy software")
added the preference to set rtm_table in dumps to RT_TABLE_COMPAT if the
table id is > 255. The table id returned on get route requests should do
the same.

Fixes: c36ba660 ("net: Allow user to get table id from route lookup")
Signed-off-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Nothing about the route lookup requires bottom half to be disabled.
Remove the local_bh_disable ... local_bh_enable around ip_route_input.
This appears to be a vestige of days gone by as it has been there
since the beginning of git time.
Signed-off-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

fl4 arg is not used; remove it.
Signed-off-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

ipmr_get_route has 1 caller and the nowait arg is 0. Remove the arg and
simplify ipmr_get_route accordingly.
Signed-off-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

rt_fill_info has only 1 caller and both of the last 2 args -- nowait
and flags -- are hardcoded to 0. Given that remove them as input arguments
and simplify rt_fill_info accordingly.
Signed-off-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

IPv4 output routes already use l3mdev device instead of loopback for dst's
if it is applicable. Change local input routes to do the same.

This fixes icmp responses for unreachable UDP ports which are directed
to the wrong table after commit 9d1a6c4e because local_input
routes use the loopback device. Moving from ingress device to loopback
loses the L3 domain causing responses based on the dst to get to lost.

Fixes: 9d1a6c4e ("net: icmp_route_lookup should use rt dev to
		       determine L3 domain")
Signed-off-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This was entirely automated, using the script by Al:

  PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*<asm/uaccess.h>'
  sed -i -e "s!$PATT!#include <linux/uaccess.h>!" \
        $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)

to do the replacement at the end of the merge window.
Requested-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit e2d118a1 ("net: inet: Support UID-based routing in IP
protocols.") made ip_do_redirect call sock_net(sk) to determine
the network namespace of the passed-in socket. This crashes if sk
is NULL.

Fix this by getting the network namespace from the skb instead.

Fixes: e2d118a1 ("net: inet: Support UID-based routing in IP protocols.")
Signed-off-by: NLorenzo Colitti <lorenzo@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

A route on the output path hitting a RTN_LOCAL route will keep the dst
associated on its way through the loopback device. On the receive path,
the dst_input() call will thus invoke the input handler of the route
created in the output path. Thus, lwt redirection for input must be done
for dsts allocated in the otuput path as well.

Also, if a route is cached in the input path, the allocated dst should
respect lwtunnel configuration on the nexthop as well.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

orig_output for IPv4 was only set for dsts which hit an input route.
Set it consistently for locally generated traffic as well to allow
lwt to continue the dst_output() path as configured by the nexthop.

Fixes: 25368623 ("lwt: Add support to redirect dst.input")
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Commit e2d118a1 ("net: inet: Support UID-based routing in IP
protocols.") made __build_flow_key call sock_net(sk) to determine
the network namespace of the passed-in socket. This crashes if sk
is NULL.

Fix this by getting the network namespace from the skb instead.

Fixes: e2d118a1 ("net: inet: Support UID-based routing in IP protocols.")
Reported-by: NErez Shitrit <erezsh@dev.mellanox.co.il>
Signed-off-by: NLorenzo Colitti <lorenzo@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In v2.6, ip_rt_redirect() calls arp_bind_neighbour() which returns 0
and then the state of the neigh for the new_gw is checked. If the state
isn't valid then the redirected route is deleted. This behavior is
maintained up to v3.5.7 by check_peer_redirect() because rt->rt_gateway
is assigned to peer->redirect_learned.a4 before calling
ipv4_neigh_lookup().

After commit 5943634f ("ipv4: Maintain redirect and PMTU info in
struct rtable again."), ipv4_neigh_lookup() is performed without the
rt_gateway assigned to the new_gw. In the case when rt_gateway (old_gw)
isn't zero, the function uses it as the key. The neigh is most likely
valid since the old_gw is the one that sends the ICMP redirect message.
Then the new_gw is assigned to fib_nh_exception. The problem is: the
new_gw ARP may never gets resolved and the traffic is blackholed.

So, use the new_gw for neigh lookup.

Changes from v1:
 - use __ipv4_neigh_lookup instead (per Eric Dumazet).

Fixes: 5943634f ("ipv4: Maintain redirect and PMTU info in struct rtable again.")
Signed-off-by: NStephen Suryaputra Lin <ssurya@ieee.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>