linux-stable.git/net/ipv4, branch v5.4.90

nexthop: Unlink nexthop group entry in error path

2021-01-17T13:05:32+00:00

[ Upstream commit 7b01e53eee6dce7a8a6736e06b99b68cd0cc7a27 ]

In case of error, remove the nexthop group entry from the list to which
it was previously added.

Fixes: 430a049190de ("nexthop: Add support for nexthop groups")
Signed-off-by: Ido Schimmel 
Reviewed-by: Petr Machata 
Reviewed-by: David Ahern 
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

nexthop: Fix off-by-one error in error path

2021-01-17T13:05:32+00:00

[ Upstream commit 07e61a979ca4dddb3661f59328b3cd109f6b0070 ]

A reference was not taken for the current nexthop entry, so do not try
to put it in the error path.

Fixes: 430a049190de ("nexthop: Add support for nexthop groups")
Signed-off-by: Ido Schimmel 
Reviewed-by: Petr Machata 
Reviewed-by: David Ahern 
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

net: ip: always refragment ip defragmented packets

2021-01-17T13:05:32+00:00

[ Upstream commit bb4cc1a18856a73f0ff5137df0c2a31f4c50f6cf ]

Conntrack reassembly records the largest fragment size seen in IPCB.
However, when this gets forwarded/transmitted, fragmentation will only
be forced if one of the fragmented packets had the DF bit set.

In that case, a flag in IPCB will force fragmentation even if the
MTU is large enough.

This should work fine, but this breaks with ip tunnels.
Consider client that sends a UDP datagram of size X to another host.

The client fragments the datagram, so two packets, of size y and z, are
sent. DF bit is not set on any of these packets.

Middlebox netfilter reassembles those packets back to single size-X
packet, before routing decision.

packet-size-vs-mtu checks in ip_forward are irrelevant, because DF bit
isn't set.  At output time, ip refragmentation is skipped as well
because x is still smaller than the mtu of the output device.

If ttransmit device is an ip tunnel, the packet size increases to
x+overhead.

Also, tunnel might be configured to force DF bit on outer header.

In this case, packet will be dropped (exceeds MTU) and an ICMP error is
generated back to sender.

But sender already respects the announced MTU, all the packets that
it sent did fit the announced mtu.

Force refragmentation as per original sizes unconditionally so ip tunnel
will encapsulate the fragments instead.

The only other solution I see is to place ip refragmentation in
the ip_tunnel code to handle this case.

Fixes: d6b915e29f4ad ("ip_fragment: don't forward defragmented DF packet")
Reported-by: Christian Perle 
Signed-off-by: Florian Westphal 
Acked-by: Pablo Neira Ayuso 
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

net: fix pmtu check in nopmtudisc mode

2021-01-17T13:05:32+00:00

[ Upstream commit 50c661670f6a3908c273503dfa206dfc7aa54c07 ]

For some reason ip_tunnel insist on setting the DF bit anyway when the
inner header has the DF bit set, EVEN if the tunnel was configured with
'nopmtudisc'.

This means that the script added in the previous commit
cannot be made to work by adding the 'nopmtudisc' flag to the
ip tunnel configuration. Doing so breaks connectivity even for the
without-conntrack/netfilter scenario.

When nopmtudisc is set, the tunnel will skip the mtu check, so no
icmp error is sent to client. Then, because inner header has DF set,
the outer header gets added with DF bit set as well.

IP stack then sends an error to itself because the packet exceeds
the device MTU.

Fixes: 23a3647bc4f93 ("ip_tunnels: Use skb-len to PMTU check.")
Cc: Stefano Brivio 
Signed-off-by: Florian Westphal 
Acked-by: Pablo Neira Ayuso 
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

netfilter: x_tables: Update remaining dereference to RCU

2021-01-12T19:16:24+00:00

commit 443d6e86f821a165fae3fc3fc13086d27ac140b1 upstream.

This fixes the dereference to fetch the RCU pointer when holding
the appropriate xtables lock.

Reported-by: kernel test robot 
Fixes: cc00bcaa5899 ("netfilter: x_tables: Switch synchronization to RCU")
Signed-off-by: Subash Abhinov Kasiviswanathan 
Reviewed-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso 
Signed-off-by: Greg Kroah-Hartman

erspan: fix version 1 check in gre_parse_header()

2021-01-12T19:16:15+00:00

[ Upstream commit 085c7c4e1c0e50d90b7d90f61a12e12b317a91e2 ]

Both version 0 and version 1 use ETH_P_ERSPAN, but version 0 does not
have an erspan header. So the check in gre_parse_header() is wrong,
we have to distinguish version 1 from version 0.

We can just check the gre header length like is_erspan_type1().

Fixes: cb73ee40b1b3 ("net: ip_gre: use erspan key field for tunnel lookup")
Reported-by: syzbot+f583ce3d4ddf9836b27a@syzkaller.appspotmail.com
Cc: William Tu 
Cc: Lorenzo Bianconi 
Signed-off-by: Cong Wang 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

ipv4: Ignore ECN bits for fib lookups in fib_compute_spec_dst()

2021-01-12T19:16:14+00:00

[ Upstream commit 21fdca22eb7df2a1e194b8adb812ce370748b733 ]

RT_TOS() only clears one of the ECN bits. Therefore, when
fib_compute_spec_dst() resorts to a fib lookup, it can return
different results depending on the value of the second ECN bit.

For example, ECT(0) and ECT(1) packets could be treated differently.

  $ ip netns add ns0
  $ ip netns add ns1
  $ ip link add name veth01 netns ns0 type veth peer name veth10 netns ns1
  $ ip -netns ns0 link set dev lo up
  $ ip -netns ns1 link set dev lo up
  $ ip -netns ns0 link set dev veth01 up
  $ ip -netns ns1 link set dev veth10 up

  $ ip -netns ns0 address add 192.0.2.10/24 dev veth01
  $ ip -netns ns1 address add 192.0.2.11/24 dev veth10

  $ ip -netns ns1 address add 192.0.2.21/32 dev lo
  $ ip -netns ns1 route add 192.0.2.10/32 tos 4 dev veth10 src 192.0.2.21
  $ ip netns exec ns1 sysctl -wq net.ipv4.icmp_echo_ignore_broadcasts=0

With TOS 4 and ECT(1), ns1 replies using source address 192.0.2.21
(ping uses -Q to set all TOS and ECN bits):

  $ ip netns exec ns0 ping -c 1 -b -Q 5 192.0.2.255
  [...]
  64 bytes from 192.0.2.21: icmp_seq=1 ttl=64 time=0.544 ms

But with TOS 4 and ECT(0), ns1 replies using source address 192.0.2.11
because the "tos 4" route isn't matched:

  $ ip netns exec ns0 ping -c 1 -b -Q 6 192.0.2.255
  [...]
  64 bytes from 192.0.2.11: icmp_seq=1 ttl=64 time=0.597 ms

After this patch the ECN bits don't affect the result anymore:

  $ ip netns exec ns0 ping -c 1 -b -Q 6 192.0.2.255
  [...]
  64 bytes from 192.0.2.21: icmp_seq=1 ttl=64 time=0.591 ms

Fixes: 35ebf65e851c ("ipv4: Create and use fib_compute_spec_dst() helper.")
Signed-off-by: Guillaume Nault 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

netfilter: x_tables: Switch synchronization to RCU

2020-12-30T10:50:54+00:00

[ Upstream commit cc00bcaa589914096edef7fb87ca5cee4a166b5c ]

When running concurrent iptables rules replacement with data, the per CPU
sequence count is checked after the assignment of the new information.
The sequence count is used to synchronize with the packet path without the
use of any explicit locking. If there are any packets in the packet path using
the table information, the sequence count is incremented to an odd value and
is incremented to an even after the packet process completion.

The new table value assignment is followed by a write memory barrier so every
CPU should see the latest value. If the packet path has started with the old
table information, the sequence counter will be odd and the iptables
replacement will wait till the sequence count is even prior to freeing the
old table info.

However, this assumes that the new table information assignment and the memory
barrier is actually executed prior to the counter check in the replacement
thread. If CPU decides to execute the assignment later as there is no user of
the table information prior to the sequence check, the packet path in another
CPU may use the old table information. The replacement thread would then free
the table information under it leading to a use after free in the packet
processing context-

Unable to handle kernel NULL pointer dereference at virtual
address 000000000000008e
pc : ip6t_do_table+0x5d0/0x89c
lr : ip6t_do_table+0x5b8/0x89c
ip6t_do_table+0x5d0/0x89c
ip6table_filter_hook+0x24/0x30
nf_hook_slow+0x84/0x120
ip6_input+0x74/0xe0
ip6_rcv_finish+0x7c/0x128
ipv6_rcv+0xac/0xe4
__netif_receive_skb+0x84/0x17c
process_backlog+0x15c/0x1b8
napi_poll+0x88/0x284
net_rx_action+0xbc/0x23c
__do_softirq+0x20c/0x48c

This could be fixed by forcing instruction order after the new table
information assignment or by switching to RCU for the synchronization.

Fixes: 80055dab5de0 ("netfilter: x_tables: make xt_replace_table wait until old rules are not used anymore")
Reported-by: Sean Tranchetti 
Reported-by: kernel test robot 
Suggested-by: Florian Westphal 
Signed-off-by: Subash Abhinov Kasiviswanathan 
Signed-off-by: Pablo Neira Ayuso 
Signed-off-by: Sasha Levin

tcp: fix cwnd-limited bug for TSO deferral where we send nothing

2020-12-21T12:27:04+00:00

[ Upstream commit 299bcb55ecd1412f6df606e9dc0912d55610029e ]

When cwnd is not a multiple of the TSO skb size of N*MSS, we can get
into persistent scenarios where we have the following sequence:

(1) ACK for full-sized skb of N*MSS arrives
  -> tcp_write_xmit() transmit full-sized skb with N*MSS
  -> move pacing release time forward
  -> exit tcp_write_xmit() because pacing time is in the future

(2) TSQ callback or TCP internal pacing timer fires
  -> try to transmit next skb, but TSO deferral finds remainder of
     available cwnd is not big enough to trigger an immediate send
     now, so we defer sending until the next ACK.

(3) repeat...

So we can get into a case where we never mark ourselves as
cwnd-limited for many seconds at a time, even with
bulk/infinite-backlog senders, because:

o In case (1) above, every time in tcp_write_xmit() we have enough
cwnd to send a full-sized skb, we are not fully using the cwnd
(because cwnd is not a multiple of the TSO skb size). So every time we
send data, we are not cwnd limited, and so in the cwnd-limited
tracking code in tcp_cwnd_validate() we mark ourselves as not
cwnd-limited.

o In case (2) above, every time in tcp_write_xmit() that we try to
transmit the "remainder" of the cwnd but defer, we set the local
variable is_cwnd_limited to true, but we do not send any packets, so
sent_pkts is zero, so we don't call the cwnd-limited logic to update
tp->is_cwnd_limited.

Fixes: ca8a22634381 ("tcp: make cwnd-limited checks measurement-based, and gentler")
Reported-by: Ingemar Johansson 
Signed-off-by: Neal Cardwell 
Signed-off-by: Yuchung Cheng 
Acked-by: Soheil Hassas Yeganeh 
Signed-off-by: Eric Dumazet 
Link: https://lore.kernel.org/r/20201209035759.1225145-1-ncardwell.kernel@gmail.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

tcp: select sane initial rcvq_space.space for big MSS

2020-12-21T12:27:04+00:00

[ Upstream commit 72d05c00d7ecda85df29abd046da7e41cc071c17 ]

Before commit a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB")
small tcp_rmem[1] values were overridden by tcp_fixup_rcvbuf() to accommodate various MSS.

This is no longer the case, and Hazem Mohamed Abuelfotoh reported
that DRS would not work for MTU 9000 endpoints receiving regular (1500 bytes) frames.

Root cause is that tcp_init_buffer_space() uses tp->rcv_wnd for upper limit
of rcvq_space.space computation, while it can select later a smaller
value for tp->rcv_ssthresh and tp->window_clamp.

ss -temoi on receiver would show :

skmem:(r0,rb131072,t0,tb46080,f0,w0,o0,bl0,d0) rcv_space:62496 rcv_ssthresh:56596

This means that TCP can not increase its window in tcp_grow_window(),
and that DRS can never kick.

Fix this by making sure that rcvq_space.space is not bigger than number of bytes
that can be held in TCP receive queue.

People unable/unwilling to change their kernel can work around this issue by
selecting a bigger tcp_rmem[1] value as in :

echo "4096 196608 6291456" >/proc/sys/net/ipv4/tcp_rmem

Based on an initial report and patch from Hazem Mohamed Abuelfotoh
 https://lore.kernel.org/netdev/20201204180622.14285-1-abuehaze@amazon.com/

Fixes: a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB")
Fixes: 041a14d26715 ("tcp: start receiver buffer autotuning sooner")
Reported-by: Hazem Mohamed Abuelfotoh 
Signed-off-by: Eric Dumazet 
Acked-by: Soheil Hassas Yeganeh 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman