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Cong Wang 5c3ca9cb48 net_sched: Prevent creation of classes with TC_H_ROOT
[ Upstream commit 0c3057a5a0 ]

The function qdisc_tree_reduce_backlog() uses TC_H_ROOT as a termination
condition when traversing up the qdisc tree to update parent backlog
counters. However, if a class is created with classid TC_H_ROOT, the
traversal terminates prematurely at this class instead of reaching the
actual root qdisc, causing parent statistics to be incorrectly maintained.
In case of DRR, this could lead to a crash as reported by Mingi Cho.

Prevent the creation of any Qdisc class with classid TC_H_ROOT
(0xFFFFFFFF) across all qdisc types, as suggested by Jamal.

Reported-by: Mingi Cho <mincho@theori.io>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Fixes: 066a3b5b23 ("[NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop")
Link: https://patch.msgid.link/20250306232355.93864-2-xiyou.wangcong@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2025-03-22 12:54:13 -07:00
2024-09-01 20:43:24 -07:00
2025-03-13 13:01:42 +01:00
2024-11-07 14:14:59 -08:00
2022-09-28 09:02:20 +02:00
2025-03-13 13:02:20 +01:00
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.
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