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Sven Eckelmann 1381b021bf batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd 
commit 33ccd52f3c upstream.

The cwnd is always MSS <= cwnd <= 0x20000000. But the calculation in
batadv_tp_update_cwnd() assumes unsigned 32 bit arithmetics.

    ((mss * 8) ** 2) / (cwnd * 8)

In case cwnd is actually 0x20000000, it will be shifted by 3 bit to the
left end up at 0x100000000 or U32_MAX + 1. It will therefore wrap around
and be 0 - resulting in:

    ((mss * 8) ** 2) / 0

This is of course invalid and cannot be calculated. The calculation should
must be simplified to avoid this overflow:

   (mss ** 2) * 8 / cwnd

It will keep the precision enhancement from the scaling (by 8) but avoid
the overflow in the divisor.

In theory, there could still be an overflow in the dividend. It is at the
moment fixed to BATADV_TP_PLEN in batadv_tp_recv_ack() - so it is not an
imminent problem. But allowing it to use the whole u32 bit range, would
mean that it can still use up to 67 bits. To keep this calculation safe for
32 bit arithmetic, mss must never use more than floor((32 - 3) / 2) bits -
or in other words: must never be larger than 16383.

Cc: stable@kernel.org
Fixes: 33a3bb4a33 ("batman-adv: throughput meter implementation")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-07-04 13:39:38 +02:00
arch KVM: x86/mmu: Ensure hugepage is in by slot before checking max mapping level 2026-07-04 13:39:37 +02:00
block blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init 2026-06-19 13:33:49 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto use less confusing names for iov_iter direction initializers 2026-06-19 13:33:46 +02:00
Documentation arm64: errata: Mitigate TLBI errata on Microsoft Azure Cobalt 100 CPU 2026-06-19 13:33:50 +02:00
drivers media: vidtv: fix NULL pointer dereference in vidtv_mux_push_si 2026-07-04 13:39:37 +02:00
fs virtiofs: fix UAF on submount umount 2026-07-04 13:39:37 +02:00
include KVM: x86/mmu: Ensure hugepage is in by slot before checking max mapping level 2026-07-04 13:39:37 +02:00
init randomize_kstack: Maintain kstack_offset per task 2026-06-19 13:33:41 +02:00
io_uring io_uring/poll: fix signed comparison in io_poll_get_ownership() 2026-06-19 13:33:39 +02:00
ipc ipc/shm: serialize orphan cleanup with shm_nattch updates 2026-06-19 13:33:38 +02:00
kernel tracing/probes: Limit size of event probe to 3K 2026-06-19 13:33:44 +02:00
lib lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl() 2026-06-19 13:33:39 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/huge_memory: update file PMD counter before folio_put() 2026-06-19 13:33:49 +02:00
net batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd 2026-07-04 13:39:38 +02:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts scripts/dtc: Remove unused dts_version in dtc-lexer.l 2026-06-01 17:35:12 +02:00
security apparmor: validate default DFA states are in bounds 2026-06-19 13:33:50 +02:00
sound ALSA: hda/hdmi: Add quirk for TUXEDO IBS14G6 2026-06-19 13:33:50 +02:00
tools kselftest/arm64: signal: Skip SVE signal test if not enough VLs supported 2026-07-04 13:39:37 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Reject wrapped offset in kvm_reset_dirty_gfn() 2026-06-01 17:35:44 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.210 2026-06-19 13:33:51 +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.