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Forest Crossman 2cc651be5b usb: mon: Increase BUFF_MAX to 64 MiB to support multi-MB URBs 
[ Upstream commit 368ed48a5e ]

The usbmon binary interface currently truncates captures of large
transfers from higher-speed USB devices. Because a single event capture
is limited to one-fifth of the total buffer size, the current maximum
size of a captured URB is around 240 KiB. This is insufficient when
capturing traffic from modern devices that use transfers of several
hundred kilobytes or more, as truncated URBs can make it impossible for
user-space USB analysis tools like Wireshark to properly defragment and
reassemble higher-level protocol packets in the captured data.

The root cause of this issue is the 1200 KiB BUFF_MAX limit, which has
not been changed since the binary interface was introduced in 2006.

To resolve this issue, this patch increases BUFF_MAX to 64 MiB. The
original comment for BUFF_MAX based the limit's calculation on a
saturated 480 Mbit/s bus. Applying the same logic to a modern USB 3.2
Gen 2×2 20 Gbit/s bus (~2500 MB/s over a 20ms window) indicates the
buffer should be at least 50 MB. The new limit of 64 MiB covers that,
plus a little extra for any overhead.

With this change, both users and developers should now be able to debug
and reverse engineer modern USB devices even when running unmodified
distro kernels.

Please note that this change does not affect the default buffer size. A
larger buffer is only allocated when a user explicitly requests it via
the MON_IOCT_RING_SIZE ioctl, so the change to the maximum buffer size
should not unduly increase memory usage for users that don't
deliberately request a larger buffer.

Link: https://lore.kernel.org/CAO3ALPzdUkmMr0YMrODLeDSLZqNCkWcAP8NumuPHLjNJ8wC1kQ@mail.gmail.com
Signed-off-by: Forest Crossman <cyrozap@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/CAO3ALPxU5RzcoueC454L=WZ1qGMfAcnxm+T+p+9D8O9mcrUbCQ@mail.gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-11-13 15:37:25 -05:00
arch x86/virt/tdx: Use precalculated TDVPR page physical address 2025-11-13 15:37:20 -05:00
block blk-cgroup: fix possible deadlock while configuring policy 2025-11-13 15:36:52 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:37:14 +02:00
Documentation dt-bindings: display/msm/gmu: Update Adreno 623 bindings 2025-11-13 15:37:16 -05:00
drivers
fs allow finish_no_open(file, ERR_PTR(-E...)) 2025-11-13 15:37:25 -05:00
include scsi: ufs: core: Disable timestamp functionality if not supported 2025-11-13 15:37:25 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:37:27 +02:00
io_uring io_uring/zcrx: account niov arrays to cgroup 2025-11-13 15:36:51 -05:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel uprobe: Do not emulate/sstep original instruction when ip is changed 2025-11-13 15:36:53 -05:00
lib kunit: Enable PCI on UML without triggering WARN() 2025-11-13 15:36:51 -05:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm treewide: remove MIGRATEPAGE_SUCCESS 2025-10-29 14:10:32 +01:00
net ethernet: Extend device_get_mac_address() to use NVMEM 2025-11-13 15:37:24 -05:00
rust rust: kunit: allow cfg on tests 2025-11-13 15:36:51 -05:00
samples 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
scripts docs: kernel-doc: avoid script crash on ancient Python 2025-11-13 15:36:58 -05:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:37:28 +02:00
sound ALSA: serial-generic: remove shared static buffer 2025-11-13 15:37:22 -05:00
tools selftests/Makefile: include $(INSTALL_DEP_TARGETS) in clean target to clean net/lib dependency 2025-11-13 15:37:25 -05:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.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: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap 7 hotfixes. 4 are cc:stable and the remainder address post-6.16 issues or 2025-09-28 09:32:00 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -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: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS i2c-for-6.17-rc8 2025-09-28 13:19:23 -07:00
Makefile Linux 6.17.7 2025-11-02 22:18:05 +09:00
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.