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Peilin Ye d5049ef1f6 ip6_gre: Fix skb_under_panic in __gre6_xmit() 
[ Upstream commit ab198e1d0d ]

Feng reported an skb_under_panic BUG triggered by running
test_ip6gretap() in tools/testing/selftests/bpf/test_tunnel.sh:

[   82.492551] skbuff: skb_under_panic: text:ffffffffb268bb8e len:403 put:12 head:ffff9997c5480000 data:ffff9997c547fff8 tail:0x18b end:0x2c0 dev:ip6gretap11
<...>
[   82.607380] Call Trace:
[   82.609389]  <TASK>
[   82.611136]  skb_push.cold.109+0x10/0x10
[   82.614289]  __gre6_xmit+0x41e/0x590
[   82.617169]  ip6gre_tunnel_xmit+0x344/0x3f0
[   82.620526]  dev_hard_start_xmit+0xf1/0x330
[   82.623882]  sch_direct_xmit+0xe4/0x250
[   82.626961]  __dev_queue_xmit+0x720/0xfe0
<...>
[   82.633431]  packet_sendmsg+0x96a/0x1cb0
[   82.636568]  sock_sendmsg+0x30/0x40
<...>

The following sequence of events caused the BUG:

1. During ip6gretap device initialization, tunnel->tun_hlen (e.g. 4) is
   calculated based on old flags (see ip6gre_calc_hlen());
2. packet_snd() reserves header room for skb A, assuming
   tunnel->tun_hlen is 4;
3. Later (in clsact Qdisc), the eBPF program sets a new tunnel key for
   skb A using bpf_skb_set_tunnel_key() (see _ip6gretap_set_tunnel());
4. __gre6_xmit() detects the new tunnel key, and recalculates
   "tun_hlen" (e.g. 12) based on new flags (e.g. TUNNEL_KEY and
   TUNNEL_SEQ);
5. gre_build_header() calls skb_push() with insufficient reserved header
   room, triggering the BUG.

As sugguested by Cong, fix it by moving the call to skb_cow_head() after
the recalculation of tun_hlen.

Reproducer:

  OBJ=$LINUX/tools/testing/selftests/bpf/test_tunnel_kern.o

  ip netns add at_ns0
  ip link add veth0 type veth peer name veth1
  ip link set veth0 netns at_ns0
  ip netns exec at_ns0 ip addr add 172.16.1.100/24 dev veth0
  ip netns exec at_ns0 ip link set dev veth0 up
  ip link set dev veth1 up mtu 1500
  ip addr add dev veth1 172.16.1.200/24

  ip netns exec at_ns0 ip addr add ::11/96 dev veth0
  ip netns exec at_ns0 ip link set dev veth0 up
  ip addr add dev veth1 ::22/96
  ip link set dev veth1 up

  ip netns exec at_ns0 \
  	ip link add dev ip6gretap00 type ip6gretap seq flowlabel 0xbcdef key 2 \
  	local ::11 remote ::22

  ip netns exec at_ns0 ip addr add dev ip6gretap00 10.1.1.100/24
  ip netns exec at_ns0 ip addr add dev ip6gretap00 fc80::100/96
  ip netns exec at_ns0 ip link set dev ip6gretap00 up

  ip link add dev ip6gretap11 type ip6gretap external
  ip addr add dev ip6gretap11 10.1.1.200/24
  ip addr add dev ip6gretap11 fc80::200/24
  ip link set dev ip6gretap11 up

  tc qdisc add dev ip6gretap11 clsact
  tc filter add dev ip6gretap11 egress bpf da obj $OBJ sec ip6gretap_set_tunnel
  tc filter add dev ip6gretap11 ingress bpf da obj $OBJ sec ip6gretap_get_tunnel

  ping6 -c 3 -w 10 -q ::11

Fixes: 6712abc168 ("ip6_gre: add ip6 gre and gretap collect_md mode")
Reported-by: Feng Zhou <zhoufeng.zf@bytedance.com>
Co-developed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-27 14:38:53 +02:00
arch arm64/mm: drop HAVE_ARCH_PFN_VALID 2022-04-27 14:38:50 +02:00
block block: simplify the block device syncing code 2022-04-27 14:38:50 +02:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: xts - Add softdep on ecb 2022-04-08 14:23:55 +02:00
Documentation dt-bindings: net: snps: remove duplicate name 2022-04-20 09:34:21 +02:00
drivers igc: Fix suspending when PTM is active 2022-04-27 14:38:53 +02:00
fs gfs2: assign rgrp glock before compute_bitstructs 2022-04-27 14:38:51 +02:00
include esp: limit skb_page_frag_refill use to a single page 2022-04-27 14:38:52 +02:00
init init/main.c: return 1 from handled __setup() functions 2022-04-13 20:59:10 +02:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-08 18:34:03 +01:00
kernel dma-mapping: remove bogus test for pfn_valid from dma_map_resource 2022-04-27 14:38:50 +02:00
lib stacktrace: move filter_irq_stacks() to kernel/stacktrace.c 2022-04-13 20:59:28 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-27 14:38:51 +02:00
net ip6_gre: Fix skb_under_panic in __gre6_xmit() 2022-04-27 14:38:53 +02:00
samples samples/bpf, xdpsock: Fix race when running for fix duration of time 2022-04-08 14:23:40 +02:00
scripts gcc-plugins: latent_entropy: use /dev/urandom 2022-04-20 09:34:18 +02:00
security Fix incorrect type in assignment of ipv6 port for audit 2022-04-08 14:23:55 +02:00
sound ALSA: hda/hdmi: fix warning about PCM count when used with SOF 2022-04-27 14:38:53 +02:00
tools perf tools: Fix segfault accessing sample_id xyarray 2022-04-27 14:38:50 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: avoid NULL pointer dereference in kvm_dirty_ring_push 2022-04-13 20:59:26 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: adjust file entry for of_net.c after movement 2022-03-08 19:12:53 +01:00
Makefile Linux 5.15.35 2022-04-20 09:34:22 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.