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Forest Crossman e9d2ab8795 usb: mon: Increase BUFF_MAX to 64 MiB to support multi-MB URBs
[ Upstream commit 368ed48a5ef52e384f54d5809f0a0b79ac567479 ]

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>
2025-12-03 12:45:12 +01:00
arch mips: lantiq: xway: sysctrl: rename stp clock 2025-12-03 12:45:11 +01:00
block block: use int to store blk_stack_limits() return value 2025-10-29 13:59:46 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:11:22 +02:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-29 13:59:52 +01:00
Documentation arm64: errata: Apply workarounds for Neoverse-V3AE 2025-10-29 14:00:00 +01:00
drivers usb: mon: Increase BUFF_MAX to 64 MiB to support multi-MB URBs 2025-12-03 12:45:12 +01:00
fs allow finish_no_open(file, ERR_PTR(-E...)) 2025-12-03 12:45:12 +01:00
include net/cls_cgroup: Fix task_get_classid() during qdisc run 2025-12-03 12:45:12 +01:00
init bpfilter: match bit size of bpfilter_umh to that of the kernel 2025-07-17 18:24:51 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:02:52 +01:00
kernel uprobe: Do not emulate/sstep original instruction when ip is changed 2025-12-03 12:45:08 +01:00
lib lib/genalloc: fix device leak in of_gen_pool_get() 2025-10-29 13:59:53 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: hugetlb: avoid soft lockup when mprotect to large memory area 2025-10-29 13:59:50 +01:00
net net: call cond_resched() less often in __release_sock() 2025-12-03 12:45:11 +01:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:21:19 +02:00
scripts randstruct: gcc-plugin: Fix attribute addition 2025-09-09 18:44:01 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-29 14:00:01 +01:00
sound ALSA: usb-audio: apply quirk for MOONDROP Quark2 2025-12-03 12:45:11 +01:00
tools selftests/Makefile: include $(INSTALL_DEP_TARGETS) in clean target to clean net/lib dependency 2025-12-03 12:45:12 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-07-17 18:24:51 +02:00
virt KVM: arm64: Ignore PMCNTENSET_EL0 while checking for overflow status 2024-12-19 18:05:04 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes
.gitignore Remove *.orig pattern from .gitignore 2024-11-08 16:20:33 +01:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS platform: Add Surface platform directory 2025-06-27 11:02:56 +01:00
Makefile Linux 5.4.301 2025-10-29 14:00:02 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 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.