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[34.127.51.67]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2df6a5a4997sm19710685ad.27.2026.09.23.21.27.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 21:27:32 -0700 (PDT) From: Hui Peng To: Waiman Long , Ridong Chen , Guopeng Zhang , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= Cc: Shuah Khan , Chen Ridong , cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Hui Peng , stable@vger.kernel.org Subject: [PATCH v4 2/3] cgroup/cpuset: prevent activating local partition over remote one Date: Thu, 24 Sep 2026 04:27:28 +0000 Message-ID: <20260924042729.1908863-3-benquike@gmail.com> X-Mailer: git-send-email 2.56.0.rc1.310.g51773c2048-goog In-Reply-To: <20260924042729.1908863-1-benquike@gmail.com> References: <20260924042729.1908863-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Commit 6da580ec656a ("cgroup/cpuset: Don't allow creation of local partition over a remote one") added a check in update_prstate() to reject creating a top-level local partition whose cs->exclusive_cpus intersects subpartitions_cpus. However, if a top-level cgroup A1 has a child A1/A2 enabled as a remote partition on a subset of its exclusive CPUs (X2-3 on A1, CX2-3:P2 on A1/A2), and A1 is then set to "root" (P1, becoming "root invalid" via update_prstate() because its exclusive CPUs intersect subpartitions_cpus) followed by expanding its CPUs to include additional non-remote CPUs (CX1-3), update_cpumask() / update_exclusive_cpumask() calls validate_partition() without going through update_prstate(). Because validate_partition() does not check trialcs->exclusive_cpus against subpartitions_cpus, A1 transitions from "root invalid" to a valid local partition over the existing remote partition A1/A2 and triggers: WARNING: kernel/cgroup/cpuset.c:1943 at update_parent_effective_cpumask+0x189b/0x1fd0 Check trialcs->exclusive_cpus against subpartitions_cpus in validate_partition() when !is_partition_valid(cs), and add a regression test case to tools/testing/selftests/cgroup/test_cpuset_prs.sh. Tested in QEMU on Linux 7.3.0-rc3 using tools/testing/selftests/cgroup/test_cpuset_prs.sh. Fixes: 6da580ec656a ("cgroup/cpuset: Don't allow creation of local partition over a remote one") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Hui Peng --- kernel/cgroup/cpuset.c | 4 ++++ tools/testing/selftests/cgroup/test_cpuset_prs.sh | 2 ++ 2 files changed, 6 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 7381fa8502e7..7c5b4a8f1f3a 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2415,6 +2415,10 @@ static enum prs_errcode validate_partition(struct cpuset *cs, struct cpuset *tri if (cpumask_empty(trialcs->effective_xcpus)) return PERR_INVCPUS; + if ((parent == &top_cpuset) && !is_partition_valid(cs) && + cpumask_intersects(trialcs->exclusive_cpus, subpartitions_cpus)) + return PERR_REMOTE; + if (prstate_housekeeping_conflict(trialcs->partition_root_state, trialcs->effective_xcpus)) return PERR_HKEEPING; diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index b732078bf319..4a451350ad84 100755 --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh @@ -321,6 +321,8 @@ TEST_MATRIX=( " C1-3:P2 X4:P2 . . . X3:P2 . . 0 A1:1-2|XA1:1-3|A2:3:XA2:3 A1:P2|A2:P2 1-3" " C0-3:P2 . . C4-6 C0-4 . . . 0 A1:0-4|B1:5-6 A1:P2|B1:P0" " C0-3:P2 . . C4-6 C0-4:C0-3 . . . 0 A1:0-3|B1:4-6 A1:P2|B1:P0 0-3" + " X2-3 CX2-3:P2 . . P1:CX1-3 . . . 0 A1:1|A2:2-3|XA2:2-3 \ + A1:P-1|A2:P2 2-3" # Local partition invalidation tests " C0-3:X1-3:P2 C1-3:X2-3:P2 C2-3:X3:P2 \ -- 2.49.0