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Anton Danilov 5ac448133e ipv4: ip_gre: Fix drops of small packets in ipgre_xmit
[ Upstream commit c4a14f6d9d17ad1e41a36182dd3b8a5fd91efbd7 ]

Regression Description:

Depending on the options specified for the GRE tunnel device, small
packets may be dropped. This occurs because the pskb_network_may_pull
function fails due to the packet's insufficient length.

For example, if only the okey option is specified for the tunnel device,
original (before encapsulation) packets smaller than 28 bytes (including
the IPv4 header) will be dropped. This happens because the required
length is calculated relative to the network header, not the skb->head.

Here is how the required length is computed and checked:

* The pull_len variable is set to 28 bytes, consisting of:
  * IPv4 header: 20 bytes
  * GRE header with Key field: 8 bytes

* The pskb_network_may_pull function adds the network offset, shifting
the checkable space further to the beginning of the network header and
extending it to the beginning of the packet. As a result, the end of
the checkable space occurs beyond the actual end of the packet.

Instead of ensuring that 28 bytes are present in skb->head, the function
is requesting these 28 bytes starting from the network header. For small
packets, this requested length exceeds the actual packet size, causing
the check to fail and the packets to be dropped.

This issue affects both locally originated and forwarded packets in
DMVPN-like setups.

How to reproduce (for local originated packets):

  ip link add dev gre1 type gre ikey 1.9.8.4 okey 1.9.8.4 \
          local <your-ip> remote 0.0.0.0

  ip link set mtu 1400 dev gre1
  ip link set up dev gre1
  ip address add 192.168.13.1/24 dev gre1
  ip neighbor add 192.168.13.2 lladdr <remote-ip> dev gre1
  ping -s 1374 -c 10 192.168.13.2
  tcpdump -vni gre1
  tcpdump -vni <your-ext-iface> 'ip proto 47'
  ip -s -s -d link show dev gre1

Solution:

Use the pskb_may_pull function instead the pskb_network_may_pull.

Fixes: 80d875cfc9d3 ("ipv4: ip_gre: Avoid skb_pull() failure in ipgre_xmit()")
Signed-off-by: Anton Danilov <littlesmilingcloud@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20240924235158.106062-1-littlesmilingcloud@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-11-08 16:20:36 +01:00
arch riscv: Fix fp alignment bug in perf_callchain_user() 2024-11-08 16:20:32 +01:00
block block, bfq: don't break merge chain in bfq_split_bfqq() 2024-11-08 16:20:28 +01:00
certs
crypto crypto: aead,cipher - zeroize key buffer after use 2024-11-08 16:20:33 +01:00
Documentation ipmi: docs: don't advertise deprecated sysfs entries 2024-11-08 16:20:29 +01:00
drivers net: ethernet: lantiq_etop: fix memory disclosure 2024-11-08 16:20:36 +01:00
fs ceph: remove the incorrect Fw reference check when dirtying pages 2024-11-08 16:20:35 +01:00
include netfilter: uapi: NFTA_FLOWTABLE_HOOK is NLA_NESTED 2024-11-08 16:20:35 +01:00
init init: open /initrd.image with O_LARGEFILE 2024-04-13 12:51:36 +02:00
ipc ipc: replace costly bailout check in sysvipc_find_ipc() 2024-09-04 13:15:02 +02:00
kernel bpf: Fix bpf_strtol and bpf_strtoul helpers for 32bit 2024-11-08 16:20:31 +01:00
lib debugobjects: Fix conditions in fill_pool() 2024-11-08 16:20:34 +01:00
LICENSES
mm mm: only enforce minimum stack gap size if it's sensible 2024-11-08 16:20:35 +01:00
net ipv4: ip_gre: Fix drops of small packets in ipgre_xmit 2024-11-08 16:20:36 +01:00
samples media: rename VFL_TYPE_GRABBER to _VIDEO 2024-03-26 18:22:22 -04:00
scripts scripts: kconfig: merge_config: config files: add a trailing newline 2024-11-08 16:20:24 +01:00
security smackfs: Use rcu_assign_pointer() to ensure safe assignment in smk_set_cipso 2024-11-08 16:20:30 +01:00
sound ASoC: meson: axg-card: fix 'use-after-free' 2024-11-08 16:20:34 +01:00
tools perf time-utils: Fix 32-bit nsec parsing 2024-11-08 16:20:31 +01:00
usr
virt KVM: async_pf: Cleanup kvm_setup_async_pf() 2024-05-02 16:18:32 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Remove *.orig pattern from .gitignore 2024-11-08 16:20:33 +01:00
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-30 16:27:12 +02:00
Makefile Linux 5.4.284 2024-09-12 11:03:57 +02:00
README

Linux kernel
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