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In qdisc_tree_reduce_backlog, Qdiscs with major handle ffff: are assumed to be either root or ingress. This assumption is bogus since it's valid to create egress qdiscs with major handle ffff: Budimir Markovic found that for qdiscs like DRR that maintain an active class list, it will cause a UAF with a dangling class pointer. In066a3b5b23, the concern was to avoid iterating over the ingress qdisc since its parent is itself. The proper fix is to stop when parent TC_H_ROOT is reached because the only way to retrieve ingress is when a hierarchy which does not contain a ffff: major handle call into qdisc_lookup with TC_H_MAJ(TC_H_ROOT). In the scenario where major ffff: is an egress qdisc in any of the tree levels, the updates will also propagate to TC_H_ROOT, which then the iteration must stop. Fixes:066a3b5b23("[NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop") Reported-by: Budimir Markovic <markovicbudimir@gmail.com> Suggested-by: Jamal Hadi Salim <jhs@mojatatu.com> Tested-by: Victor Nogueira <victor@mojatatu.com> Signed-off-by: Pedro Tammela <pctammela@mojatatu.com> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com> net/sched/sch_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20241024165547.418570-1-jhs@mojatatu.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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.