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Laurent Vivier 00a39a148d usbnet: limit max_mtu based on device's hard_mtu
[ Upstream commit c7159e960f ]

The usbnet driver initializes net->max_mtu to ETH_MAX_MTU before calling
the device's bind() callback. When the bind() callback sets
dev->hard_mtu based the device's actual capability (from CDC Ethernet's
wMaxSegmentSize descriptor), max_mtu is never updated to reflect this
hardware limitation).

This allows userspace (DHCP or IPv6 RA) to configure MTU larger than the
device can handle, leading to silent packet drops when the backend sends
packet exceeding the device's buffer size.

Fix this by limiting net->max_mtu to the device's hard_mtu after the
bind callback returns.

See https://gitlab.com/qemu-project/qemu/-/issues/3268 and
    https://bugs.passt.top/attachment.cgi?bugid=189

Fixes: f77f0aee4d ("net: use core MTU range checking in USB NIC drivers")
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Link: https://bugs.passt.top/show_bug.cgi?id=189
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Link: https://patch.msgid.link/20260119075518.2774373-1-lvivier@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-01-30 10:32:19 +01:00
arch riscv: suspend: Fix stimecmp update hazard on RV32 2026-01-30 10:32:16 +01:00
block block: zero non-PI portion of auto integrity buffer 2026-01-23 11:21:16 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation fou: Don't allow 0 for FOU_ATTR_IPPROTO. 2026-01-30 10:32:12 +01:00
drivers usbnet: limit max_mtu based on device's hard_mtu 2026-01-30 10:32:19 +01:00
fs fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes() 2026-01-30 10:32:15 +01:00
include mm/hugetlb: fix hugetlb_pmd_shared() 2026-01-30 10:32:15 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/io-wq: check IO_WQ_BIT_EXIT inside work run loop 2026-01-30 10:32:15 +01:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel timekeeping: Adjust the leap state for the correct auxiliary timekeeper 2026-01-30 10:32:15 +01:00
lib lib/buildid: use __kernel_read() for sleepable context 2026-01-23 11:21:25 +01:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm: restore per-memcg proactive reclaim with !CONFIG_NUMA 2026-01-30 10:32:15 +01:00
net ipv6: annotate data-race in ndisc_router_discovery() 2026-01-30 10:32:19 +01:00
rust rust: bitops: fix missing _find_* functions on 32-bit ARM 2026-01-23 11:21:12 +01:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts kconfig: fix static linking of nconf 2026-01-30 10:32:16 +01:00
security landlock: Fix wrong type usage 2026-01-23 11:21:22 +01:00
sound ALSA: usb: Increase volume range that triggers a warning 2026-01-30 10:32:17 +01:00
tools vsock/test: Do not filter kallsyms by symbol type 2026-01-30 10:32:17 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Fix last_boosted_vcpu index assignment bug 2026-01-02 12:57:21 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.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 MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.7 2026-01-23 11:21:37 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.