Subject: CVE-2024-26882: net: ip_tunnel: make sure to pull inner header in ip_tunnel_rcv()

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net: ip_tunnel: make sure to pull inner header in ip_tunnel_rcv()

Apply the same fix than ones found in :

8d975c15c0cd ("ip6_tunnel: make sure to pull inner header in __ip6_tnl_rcv()")
1ca1ba465e55 ("geneve: make sure to pull inner header in geneve_rx()")

We have to save skb->network_header in a temporary variable
in order to be able to recompute the network_header pointer
after a pskb_inet_may_pull() call.

pskb_inet_may_pull() makes sure the needed headers are in skb->head.

syzbot reported:
BUG: KMSAN: uninit-value in __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]
 BUG: KMSAN: uninit-value in INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]
 BUG: KMSAN: uninit-value in IP_ECN_decapsulate include/net/inet_ecn.h:302 [inline]
 BUG: KMSAN: uninit-value in ip_tunnel_rcv+0xed9/0x2ed0 net/ipv4/ip_tunnel.c:409
  __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]
  INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]
  IP_ECN_decapsulate include/net/inet_ecn.h:302 [inline]
  ip_tunnel_rcv+0xed9/0x2ed0 net/ipv4/ip_tunnel.c:409
  __ipgre_rcv+0x9bc/0xbc0 net/ipv4/ip_gre.c:389
  ipgre_rcv net/ipv4/ip_gre.c:411 [inline]
  gre_rcv+0x423/0x19f0 net/ipv4/ip_gre.c:447
  gre_rcv+0x2a4/0x390 net/ipv4/gre_demux.c:163
  ip_protocol_deliver_rcu+0x264/0x1300 net/ipv4/ip_input.c:205
  ip_local_deliver_finish+0x2b8/0x440 net/ipv4/ip_input.c:233
  NF_HOOK include/linux/netfilter.h:314 [inline]
  ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254
  dst_input include/net/dst.h:461 [inline]
  ip_rcv_finish net/ipv4/ip_input.c:449 [inline]
  NF_HOOK include/linux/netfilter.h:314 [inline]
  ip_rcv+0x46f/0x760 net/ipv4/ip_input.c:569
  __netif_receive_skb_one_core net/core/dev.c:5534 [inline]
  __netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5648
  netif_receive_skb_internal net/core/dev.c:5734 [inline]
  netif_receive_skb+0x58/0x660 net/core/dev.c:5793
  tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1556
  tun_get_user+0x53b9/0x66e0 drivers/net/tun.c:2009
  tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2055
  call_write_iter include/linux/fs.h:2087 [inline]
  new_sync_write fs/read_write.c:497 [inline]
  vfs_write+0xb6b/0x1520 fs/read_write.c:590
  ksys_write+0x20f/0x4c0 fs/read_write.c:643
  __do_sys_write fs/read_write.c:655 [inline]
  __se_sys_write fs/read_write.c:652 [inline]
  __x64_sys_write+0x93/0xd0 fs/read_write.c:652
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
  __alloc_pages+0x9a6/0xe00 mm/page_alloc.c:4590
  alloc_pages_mpol+0x62b/0x9d0 mm/mempolicy.c:2133
  alloc_pages+0x1be/0x1e0 mm/mempolicy.c:2204
  skb_page_frag_refill+0x2bf/0x7c0 net/core/sock.c:2909
  tun_build_skb drivers/net/tun.c:1686 [inline]
  tun_get_user+0xe0a/0x66e0 drivers/net/tun.c:1826
  tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2055
  call_write_iter include/linux/fs.h:2087 [inline]
  new_sync_write fs/read_write.c:497 [inline]
  vfs_write+0xb6b/0x1520 fs/read_write.c:590
  ksys_write+0x20f/0x4c0 fs/read_write.c:643
  __do_sys_write fs/read_write.c:655 [inline]
  __se_sys_write fs/read_write.c:652 [inline]
  __x64_sys_write+0x93/0xd0 fs/read_write.c:652
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

The Linux kernel CVE team has assigned CVE-2024-26882 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 3.10 with commit c54419321455 and fixed in 5.4.273 with commit ec6bb01e02cb
	Issue introduced in 3.10 with commit c54419321455 and fixed in 5.10.214 with commit 77fd5294ea09
	Issue introduced in 3.10 with commit c54419321455 and fixed in 5.15.153 with commit 5c03387021cf
	Issue introduced in 3.10 with commit c54419321455 and fixed in 6.1.83 with commit 60044ab84836
	Issue introduced in 3.10 with commit c54419321455 and fixed in 6.6.23 with commit c4c857723b37
	Issue introduced in 3.10 with commit c54419321455 and fixed in 6.7.11 with commit f6723d8dbfdc
	Issue introduced in 3.10 with commit c54419321455 and fixed in 6.8.2 with commit ca914f1cdee8
	Issue introduced in 3.10 with commit c54419321455 and fixed in 6.9 with commit b0ec2abf9826
	Issue introduced in 3.10.12 with commit 27c1c98bd3b4

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26882
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/ipv4/ip_tunnel.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/ec6bb01e02cbd47781dd90775b631a1dc4bd9d2b
	https://git.kernel.org/stable/c/77fd5294ea09b21f6772ac954a121b87323cec80
	https://git.kernel.org/stable/c/5c03387021cfa3336b97e0dcba38029917a8af2a
	https://git.kernel.org/stable/c/60044ab84836359534bd7153b92e9c1584140e4a
	https://git.kernel.org/stable/c/c4c857723b37c20651300b3de4ff25059848b4b0
	https://git.kernel.org/stable/c/f6723d8dbfdc10c784a56748f86a9a3cd410dbd5
	https://git.kernel.org/stable/c/ca914f1cdee8a85799942c9b0ce5015bbd6844e1
	https://git.kernel.org/stable/c/b0ec2abf98267f14d032102551581c833b0659d3