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Willem de Bruijn d5cba7730d 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 2025-04-25 10:45:21 +02:00
arch arm64: cputype: Add QCOM_CPU_PART_KRYO_3XX_GOLD 2025-04-25 10:45:10 +02:00
block block: fix 'kmem_cache of name 'bio-108' already exists' 2025-03-22 12:50:44 -07:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: ecc - Prevent ecc_digits_from_bytes from reading too many bytes 2025-01-09 13:31:52 +01:00
Documentation dt-bindings: vendor-prefixes: add GOcontroll 2025-04-10 14:37:27 +02:00
drivers pwm: fsl-ftm: Handle clk_get_rate() returning 0 2025-04-25 10:45:21 +02:00
fs ext4: ignore xattrs past end 2025-04-25 10:45:16 +02:00
include tpm, tpm_tis: Workaround failed command reception on Infineon devices 2025-04-25 10:45:20 +02:00
init rust: Disallow BTF generation with Rust + LTO 2025-03-22 12:50:48 -07:00
io_uring io_uring: fix error pbuf checking 2025-03-22 12:50:45 -07:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel tracing: probe-events: Add comments about entry data storing code 2025-04-25 10:45:20 +02:00
lib zstd: Increase DYNAMIC_BMI2 GCC version cutoff from 4.8 to 11.0 to work around compiler segfault 2025-04-25 10:45:11 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm x86/mm/pat: Fix VM_PAT handling when fork() fails in copy_page_range() 2025-04-10 14:37:30 +02:00
net bpf: support SKF_NET_OFF and SKF_LL_OFF on skb frags 2025-04-25 10:45:21 +02:00
rust rust: lockdep: Remove support for dynamically allocated LockClassKeys 2025-03-22 12:50:50 -07:00
samples tracing: Allow creating instances with specified system events 2025-04-10 14:37:41 +02:00
scripts selinux: Chain up tool resolving errors in install_policy.sh 2025-04-10 14:37:26 +02:00
security smack: dont compile ipv6 code unless ipv6 is configured 2025-04-10 14:37:25 +02:00
sound ASoC: amd: yc: update quirk data for new Lenovo model 2025-04-25 10:45:13 +02:00
tools ktest: Fix Test Failures Due to Missing LOG_FILE Directories 2025-04-25 10:45:20 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 12:58:38 +01:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.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 USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
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 membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.87 2025-04-10 14:37:44 +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.