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Antoine Tenart 4615228a50 netfilter: bridge: reset skb->pkt_type after NF_INET_POST_ROUTING traversal
[ Upstream commit 44f64f23bae2f0fad25503bc7ab86cd08d04cd47 ]

Netfilter changes PACKET_OTHERHOST to PACKET_HOST before invoking the
hooks as, while it's an expected value for a bridge, routing expects
PACKET_HOST. The change is undone later on after hook traversal. This
can be seen with pairs of functions updating skb>pkt_type and then
reverting it to its original value:

For hook NF_INET_PRE_ROUTING:
  setup_pre_routing / br_nf_pre_routing_finish

For hook NF_INET_FORWARD:
  br_nf_forward_ip / br_nf_forward_finish

But the third case where netfilter does this, for hook
NF_INET_POST_ROUTING, the packet type is changed in br_nf_post_routing
but never reverted. A comment says:

  /* We assume any code from br_dev_queue_push_xmit onwards doesn't care
   * about the value of skb->pkt_type. */

But when having a tunnel (say vxlan) attached to a bridge we have the
following call trace:

  br_nf_pre_routing
  br_nf_pre_routing_ipv6
     br_nf_pre_routing_finish
  br_nf_forward_ip
     br_nf_forward_finish
  br_nf_post_routing           <- pkt_type is updated to PACKET_HOST
     br_nf_dev_queue_xmit      <- but not reverted to its original value
  vxlan_xmit
     vxlan_xmit_one
        skb_tunnel_check_pmtu  <- a check on pkt_type is performed

In this specific case, this creates issues such as when an ICMPv6 PTB
should be sent back. When CONFIG_BRIDGE_NETFILTER is enabled, the PTB
isn't sent (as skb_tunnel_check_pmtu checks if pkt_type is PACKET_HOST
and returns early).

If the comment is right and no one cares about the value of
skb->pkt_type after br_dev_queue_push_xmit (which isn't true), resetting
it to its original value should be safe.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Reviewed-by: Florian Westphal <fw@strlen.de>
Link: https://lore.kernel.org/r/20201123174902.622102-1-atenart@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-12-08 10:40:24 +01:00
arch x86/resctrl: Add necessary kernfs_put() calls to prevent refcount leak 2020-12-02 08:49:55 +01:00
block
certs
crypto
Documentation xtensa: fix TLBTEMP area placement 2020-11-24 13:29:22 +01:00
drivers staging/octeon: fix up merge error 2020-12-08 10:40:24 +01:00
fs efivarfs: revert "fix memory leak in efivarfs_create()" 2020-12-02 08:49:53 +01:00
include bonding: wait for sysfs kobject destruction before freeing struct slave 2020-12-08 10:40:24 +01:00
init
ipc
kernel sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list 2020-12-08 10:40:24 +01:00
lib
LICENSES
mm mm, page_alloc: skip ->waternark_boost for atomic order-0 allocations 2020-11-24 13:29:24 +01:00
net netfilter: bridge: reset skb->pkt_type after NF_INET_POST_ROUTING traversal 2020-12-08 10:40:24 +01:00
samples
scripts
security ima: extend boot_aggregate with kernel measurements 2020-12-08 10:40:24 +01:00
sound ASoC: Intel: Skylake: Automatic DMIC format configuration according to information from NHLT 2020-12-02 08:49:57 +01:00
tools perf probe: Fix to die_entrypc() returns error correctly 2020-12-02 08:49:54 +01:00
usr
virt KVM: arm64: vgic-v3: Drop the reporting of GICR_TYPER.Last for userspace 2020-12-02 08:49:46 +01:00
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Makefile Linux 5.4.81 2020-12-02 08:49:57 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.