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Wed, 22 Apr 2026 09:20:32 -0700 (PDT) Received: from SLSGDTSWING002.tail0ac356.ts.net ([129.126.109.177]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b5fab0cdd1sm170335445ad.38.2026.04.22.09.20.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2026 09:20:31 -0700 (PDT) From: Weiming Shi To: vinicius.gomes@intel.com, jhs@mojatatu.com, jiri@resnulli.us Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, vladimir.oltean@nxp.com, shuah@kernel.org, xmei5@asu.edu, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Weiming Shi Subject: [PATCH net v5 0/2] net/sched: taprio: fix NULL pointer dereference in class dump Date: Thu, 23 Apr 2026 00:19:57 +0800 Message-ID: <20260422161958.2517539-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Fix a NULL pointer dereference in taprio_dump_class() reachable by an unprivileged local user on kernels with unprivileged user namespaces enabled and CONFIG_NET_SCH_TAPRIO=y. The bug allows a local DoS via a crafted sequence of taprio child-qdisc graft, delete, and class dump. Patch 1/2 is the fix: replace NULL entries in q->qdiscs[] with the global &noop_qdisc singleton so that control-plane dump paths, as well as the existing NULL guards in the data-plane enqueue/dequeue paths, cannot deref a NULL child qdisc. Patch 2/2 is a tdc regression test that drives the graft + delete + class-dump sequence on a multi-queue netdevsim device. It panics the vulnerable kernel and passes on the fixed one. v5: only call qdisc_put(*old) when *old is non-NULL and not &noop_qdisc (Paolo). v4: https://lore.kernel.org/netdev/20260416185501.647884-3-bestswngs@gmail.com/ add selftests/tc-testing regression test (patch 2/2) (Jamal). add Assisted-by tag. v3: https://lore.kernel.org/netdev/20260414104311.74115-2-bestswngs@gmail.com/ fix broken patch v2: https://lore.kernel.org/netdev/20260410153902.955227-2-bestswngs@gmail.com/ also update NULL guards in taprio_enqueue() and taprio_dequeue_from_txq() to avoid qlen/backlog inflation (Paolo). v1: https://lore.kernel.org/netdev/20260330102904.2677818-5-bestswngs@gmail.com/ Weiming Shi (2): net/sched: taprio: fix NULL pointer dereference in class dump selftests/tc-testing: add taprio test for class dump after child delete net/sched/sch_taprio.c | 13 ++++++---- .../tc-testing/tc-tests/qdiscs/taprio.json | 26 +++++++++++++++++++ 2 files changed, 34 insertions(+), 5 deletions(-) -- 2.43.0