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A mirror of the official Linux kernel repository just in case
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Jakub Sitnicki 30b03f2a05 udp: Fall back to software USO if IPv6 extension headers are present 
In commit 10154dbded ("udp: Allow GSO transmit from devices with no
checksum offload") we have intentionally allowed UDP GSO packets marked
CHECKSUM_NONE to pass to the GSO stack, so that they can be segmented and
checksummed by a software fallback when the egress device lacks these
features.

What was not taken into consideration is that a CHECKSUM_NONE skb can be
handed over to the GSO stack also when the egress device advertises the
tx-udp-segmentation / NETIF_F_GSO_UDP_L4 feature.

This will happen when there are IPv6 extension headers present, which we
check for in __ip6_append_data(). Syzbot has discovered this scenario,
producing a warning as below:

  ip6tnl0: caps=(0x00000006401d7869, 0x00000006401d7869)
  WARNING: CPU: 0 PID: 5112 at net/core/dev.c:3293 skb_warn_bad_offload+0x166/0x1a0 net/core/dev.c:3291
  Modules linked in:
  CPU: 0 PID: 5112 Comm: syz-executor391 Not tainted 6.10.0-rc7-syzkaller-01603-g80ab5445da62 #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
  RIP: 0010:skb_warn_bad_offload+0x166/0x1a0 net/core/dev.c:3291
  [...]
  Call Trace:
   <TASK>
   __skb_gso_segment+0x3be/0x4c0 net/core/gso.c:127
   skb_gso_segment include/net/gso.h:83 [inline]
   validate_xmit_skb+0x585/0x1120 net/core/dev.c:3661
   __dev_queue_xmit+0x17a4/0x3e90 net/core/dev.c:4415
   neigh_output include/net/neighbour.h:542 [inline]
   ip6_finish_output2+0xffa/0x1680 net/ipv6/ip6_output.c:137
   ip6_finish_output+0x41e/0x810 net/ipv6/ip6_output.c:222
   ip6_send_skb+0x112/0x230 net/ipv6/ip6_output.c:1958
   udp_v6_send_skb+0xbf5/0x1870 net/ipv6/udp.c:1292
   udpv6_sendmsg+0x23b3/0x3270 net/ipv6/udp.c:1588
   sock_sendmsg_nosec net/socket.c:730 [inline]
   __sock_sendmsg+0xef/0x270 net/socket.c:745
   ____sys_sendmsg+0x525/0x7d0 net/socket.c:2585
   ___sys_sendmsg net/socket.c:2639 [inline]
   __sys_sendmmsg+0x3b2/0x740 net/socket.c:2725
   __do_sys_sendmmsg net/socket.c:2754 [inline]
   __se_sys_sendmmsg net/socket.c:2751 [inline]
   __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2751
   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
   [...]
   </TASK>

We are hitting the bad offload warning because when an egress device is
capable of handling segmentation offload requested by
skb_shinfo(skb)->gso_type, the chain of gso_segment callbacks won't produce
any segment skbs and return NULL. See the skb_gso_ok() branch in
{__udp,tcp,sctp}_gso_segment helpers.

To fix it, force a fallback to software USO when processing a packet with
IPv6 extension headers, since we don't know if these can checksummed by
all devices which offer USO.

Fixes: 10154dbded ("udp: Allow GSO transmit from devices with no checksum offload")
Reported-by: syzbot+e15b7e15b8a751a91d9a@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000e1609a061d5330ce@google.com/
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://patch.msgid.link/20240808-udp-gso-egress-from-tunnel-v4-2-f5c5b4149ab9@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-08-09 21:58:08 -07:00
arch LoongArch: KVM: Remove undefined a6 argument comment for kvm_hypercall() 2024-08-07 17:37:14 +08:00
block block: fix deadlock between sd_remove & sd_release 2024-07-24 09:51:21 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto crypto: testmgr - generate power-of-2 lengths more often 2024-07-13 11:50:28 +12:00
Documentation platform-drivers-x86 for v6.11-2 2024-08-06 07:52:10 -07:00
drivers gtp: pull network headers in gtp_dev_xmit() 2024-08-09 21:56:44 -07:00
fs tracing fixes for v6.11: 2024-08-08 13:32:59 -07:00
include Including fixes from bluetooth. 2024-08-08 13:51:44 -07:00
init rust: SHADOW_CALL_STACK is incompatible with Rust 2024-08-01 16:15:03 +01:00
io_uring io_uring: remove unused local list heads in NAPI functions 2024-07-30 06:20:20 -06:00
ipc sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
kernel tracing fixes for v6.11: 2024-08-08 13:32:59 -07:00
lib minmax: don't use max() in situations that want a C constant expression 2024-07-28 20:23:27 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 9 hotfixes. 5 are cc:stable, 4 either pertain to post-6.10 material or 2024-08-08 07:32:20 -07:00
net udp: Fall back to software USO if IPv6 extension headers are present 2024-08-09 21:58:08 -07:00
rust Rust changes for v6.11 2024-07-27 13:44:54 -07:00
samples Driver core changes for 6.11-rc1 2024-07-25 10:42:22 -07:00
scripts syscalls: fix syscall macros for newfstat/newfstatat 2024-08-02 15:20:47 +02:00
security apparmor-pr-2024-07-24 PR 2024-07-25 2024-07-27 13:28:39 -07:00
sound sound fixes for 6.11-rc2 2024-08-02 09:04:57 -07:00
tools Including fixes from bluetooth. 2024-08-08 13:51:44 -07:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: guest_memfd: abstract how prepared folios are recorded 2024-07-26 14:46:15 -04:00
.clang-format Docs: Move clang-format from process/ to dev-tools/ 2024-06-26 16:36:00 -06:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: add script and target to generate pacman package 2024-07-22 01:24:22 +09:00
.mailmap mailmap: update entry for David Heidelberg 2024-08-07 18:33:56 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS tracing: Update of MAINTAINERS and CREDITS file 2024-07-18 14:08:42 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Including fixes from bluetooth. 2024-08-08 13:51:44 -07:00
Makefile Linux 6.11-rc2 2024-08-04 13:50:53 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.