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Willem de Bruijn 806908d5d9 bpf: support SKF_NET_OFF and SKF_LL_OFF on skb frags 
[ Upstream commit d4bac0288a ]

Classic BPF socket filters with SKB_NET_OFF and SKB_LL_OFF fail to
read when these offsets extend into frags.

This has been observed with iwlwifi and reproduced with tun with
IFF_NAPI_FRAGS. The below straightforward socket filter on UDP port,
applied to a RAW socket, will silently miss matching packets.

    const int offset_proto = offsetof(struct ip6_hdr, ip6_nxt);
    const int offset_dport = sizeof(struct ip6_hdr) + offsetof(struct udphdr, dest);
    struct sock_filter filter_code[] = {
            BPF_STMT(BPF_LD  + BPF_B   + BPF_ABS, SKF_AD_OFF + SKF_AD_PKTTYPE),
            BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, PACKET_HOST, 0, 4),
            BPF_STMT(BPF_LD  + BPF_B   + BPF_ABS, SKF_NET_OFF + offset_proto),
            BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 2),
            BPF_STMT(BPF_LD  + BPF_H   + BPF_ABS, SKF_NET_OFF + offset_dport),

This is unexpected behavior. Socket filter programs should be
consistent regardless of environment. Silent misses are
particularly concerning as hard to detect.

Use skb_copy_bits for offsets outside linear, same as done for
non-SKF_(LL|NET) offsets.

Offset is always positive after subtracting the reference threshold
SKB_(LL|NET)_OFF, so is always >= skb_(mac|network)_offset. The sum of
the two is an offset against skb->data, and may be negative, but it
cannot point before skb->head, as skb_(mac|network)_offset would too.

This appears to go back to when frag support was introduced to
sk_run_filter in linux-2.4.4, before the introduction of git.

The amount of code change and 8/16/32 bit duplication are unfortunate.
But any attempt I made to be smarter saved very few LoC while
complicating the code.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Link: https://lore.kernel.org/netdev/20250122200402.3461154-1-maze@google.com/
Link: https://elixir.bootlin.com/linux/2.4.4/source/net/core/filter.c#L244
Reported-by: Matt Moeller <moeller.matt@gmail.com>
Co-developed-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://lore.kernel.org/r/20250408132833.195491-2-willemdebruijn.kernel@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-04-20 10:15:28 +02:00
arch arm64: cputype: Add QCOM_CPU_PART_KRYO_3XX_GOLD 2025-04-20 10:15:12 +02:00
block block: fix 'kmem_cache of name 'bio-108' already exists' 2025-03-22 12:54:21 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Fix larval relookup type and mask 2025-04-10 14:39:20 +02:00
Documentation ata: libata-core: Add 'external' to the libata.force kernel parameter 2025-04-20 10:15:16 +02:00
drivers pwm: fsl-ftm: Handle clk_get_rate() returning 0 2025-04-20 10:15:28 +02:00
fs erofs: set error to bio if file-backed IO fails 2025-04-20 10:15:28 +02:00
include tpm, tpm_tis: Workaround failed command reception on Infineon devices 2025-04-20 10:15:27 +02:00
init ARM: 9443/1: Require linker to support KEEP within OVERLAY for DCE 2025-04-10 14:39:40 +02:00
io_uring io_uring/net: fix sendzc double notif flush 2025-03-28 22:03:32 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel tracing: probe-events: Add comments about entry data storing code 2025-04-20 10:15:27 +02:00
lib zstd: Increase DYNAMIC_BMI2 GCC version cutoff from 4.8 to 11.0 to work around compiler segfault 2025-04-20 10:15:12 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: zswap: fix crypto_free_acomp() deadlock in zswap_cpu_comp_dead() 2025-04-10 14:39:40 +02:00
net
rust rust: Fix enabling Rust and building with GCC for LoongArch 2025-04-10 14:39:36 +02:00
samples rust: treewide: switch to the kernel Vec type 2025-03-13 13:01:46 +01:00
scripts kbuild: deb-pkg: don't set KBUILD_BUILD_VERSION unconditionally 2025-04-10 14:39:35 +02:00
security smack: ipv4/ipv6: tcp/dccp/sctp: fix incorrect child socket label 2025-04-10 14:39:10 +02:00
sound ASoC: amd: yc: update quirk data for new Lenovo model 2025-04-20 10:15:15 +02:00
tools ktest: Fix Test Failures Due to Missing LOG_FILE Directories 2025-04-20 10:15:27 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2025-03-13 13:01:42 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.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 MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
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 MAINTAINERS: add entry for the Rust alloc module 2025-03-13 13:01:47 +01:00
Makefile Linux 6.12.23 2025-04-10 14:39:41 +02:00
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.