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Eric Dumazet 110a47efcf net_sched: red: fix a race in __red_change()
[ Upstream commit 85a3e0ede3 ]

Gerrard Tai reported a race condition in RED, whenever SFQ perturb timer
fires at the wrong time.

The race is as follows:

CPU 0                                 CPU 1
[1]: lock root
[2]: qdisc_tree_flush_backlog()
[3]: unlock root
 |
 |                                    [5]: lock root
 |                                    [6]: rehash
 |                                    [7]: qdisc_tree_reduce_backlog()
 |
[4]: qdisc_put()

This can be abused to underflow a parent's qlen.

Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog()
should fix the race, because all packets will be purged from the qdisc
before releasing the lock.

Fixes: 0c8d13ac96 ("net: sched: red: delay destroying child qdisc on replace")
Reported-by: Gerrard Tai <gerrard.tai@starlabs.sg>
Suggested-by: Gerrard Tai <gerrard.tai@starlabs.sg>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250611111515.1983366-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-06-27 11:05:20 +01:00
arch powerpc/vas: Return -EINVAL if the offset is non-zero in mmap() 2025-06-27 11:05:19 +01:00
block block: fix direct io NOWAIT flag not work 2025-05-22 14:08:26 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: xts - Only add ecb if it is not already there 2025-06-27 11:05:10 +01:00
Documentation x86/bugs: Make spectre user default depend on MITIGATION_SPECTRE_V2 2025-06-04 14:37:59 +02:00
drivers net/mlx5: Fix return value when searching for existing flow group 2025-06-27 11:05:20 +01:00
fs do_change_type(): refuse to operate on unmounted/not ours mounts 2025-06-27 11:05:18 +01:00
include net: Fix TOCTOU issue in sk_is_readable() 2025-06-27 11:05:20 +01:00
init sched/isolation: Make CONFIG_CPU_ISOLATION depend on CONFIG_SMP 2025-05-02 07:44:36 +02:00
io_uring io_uring: fix possible deadlock in io_register_iowq_max_workers() 2024-11-17 15:06:25 +01:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel bpf: Avoid __bpf_prog_ret0_warn when jit fails 2025-06-27 11:05:14 +01:00
lib crypto: lzo - Fix compression buffer overrun 2025-06-04 14:37:58 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/page_alloc.c: avoid infinite retries caused by cpuset race 2025-06-04 14:38:06 +02:00
net net_sched: red: fix a race in __red_change() 2025-06-27 11:05:20 +01:00
samples samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora 2025-06-04 14:37:54 +02:00
scripts kbuild: fix argument parsing in scripts/config 2025-06-04 14:37:57 +02:00
security smack: recognize ipv4 CIPSO w/o categories 2025-06-04 14:38:02 +02:00
sound ALSA: pcm: Fix race of buffer access at PCM OSS layer 2025-06-04 14:38:06 +02:00
tools perf record: Fix incorrect --user-regs comments 2025-06-27 11:05:16 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-10-22 15:40:41 +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 trace: Relocate event helper files 2024-04-10 16:19:24 +02:00
Makefile Linux 5.15.185 2025-06-04 14:38:08 +02:00
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.