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[34.127.51.67]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e55b83602sm5635853a91.1.2026.09.20.01.23.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 20 Sep 2026 01:23:37 -0700 (PDT) From: Hui Peng To: Tejun Heo , Johannes Weiner , Waiman Long , Ridong Chen , Guopeng Zhang Cc: Michal Koutny , Shuah Khan , cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Hui Peng Subject: [PATCH v2 2/2] cgroup/cpuset: prevent local partition activation over remote partition and sibling xcpus conflict Date: Sun, 20 Sep 2026 08:23:35 +0000 Message-ID: <20260920082335.257680-2-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog In-Reply-To: <20260920082335.257680-1-benquike@gmail.com> References: <139d9231-4723-4365-9af7-8142e6581ede@linux.dev> <20260920082335.257680-1-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, two paths still allow overlapping exclusive CPU ownership between a top-level local partition and a remote partition or sibling: 1. If a top-level cgroup A1 has cpuset.cpus.exclusive set, is first set to "root" while cpuset.cpus is empty (becoming "root invalid"), has a child A1/A2 enabled as a remote partition on those exclusive CPUs, and then receives CPUs via A1/cpuset.cpus, update_cpumasks_hier() 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:1866 at update_parent_effective_cpumask+0x54a/0x8a0 2. In cpus_excl_conflict(), when a valid local partition A1 uses implicit exclusive CPUs (cpuset.cpus set without cpuset.cpus.exclusive, so sibling->exclusive_cpus is empty while sibling->effective_xcpus is populated), a sibling cgroup B1 can still set cpuset.cpus.exclusive on the same CPUs because cpus_excl_conflict() only checks sibling->exclusive_cpus. Fix these issues by: - Checking trialcs->exclusive_cpus against subpartitions_cpus in validate_partition() when !is_partition_valid(cs). - Falling back to sibling->effective_xcpus in cpus_excl_conflict() when sibling->exclusive_cpus is empty. - Adding regression test cases for both paths 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 Signed-off-by: Hui Peng --- Changes in v2: - Split from the remote_partition_enable() fix into patch 2/2. - Check trialcs->exclusive_cpus (rather than effective_xcpus) in validate_partition() when !is_partition_valid(cs) so sibling local partitions with overlapping cpuset.cpus continue to share remaining available CPUs as expected by test_cpuset_prs.sh. - Add regression tests to tools/testing/selftests/cgroup/test_cpuset_prs.sh. kernel/cgroup/cpuset.c | 9 ++++++++- tools/testing/selftests/cgroup/test_cpuset_prs.sh | 3 +++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 7381fa8502e7..f46a51f07938 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -713,7 +713,10 @@ static inline bool cpus_excl_conflict(struct cpuset *trial, struct cpuset *sibli return true; /* Exclusive_cpus cannot intersect */ - return cpumask_intersects(trial->exclusive_cpus, sibling->exclusive_cpus); + return cpumask_intersects(trial->exclusive_cpus, + cpumask_empty(sibling->exclusive_cpus) + ? sibling->effective_xcpus + : sibling->exclusive_cpus); } static inline bool mems_excl_conflict(struct cpuset *cs1, struct cpuset *cs2) @@ -2415,6 +2418,10 @@ 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..f62155cf6162 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" + " X1-3:P1 CX2-3:P2 . . C1-3 . . . 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 \ @@ -443,6 +445,7 @@ TEST_MATRIX=( # Changes to cpuset.cpus.exclusive that violate exclusivity rule is rejected " C0-3 . . C4-5 X0-3 . . X3-5 1 A1:0-3|B1:4-5" + " C0-3:P1 . . C4-5 . . . X3-5 1 A1:0-3|B1:4-5 A1:P1|B1:P0" # cpuset.cpus.exclusive cannot be set to a superset of sibling's cpuset.cpus " C0-3 . . C4-5 X3-5 . . . 1 A1:0-3|B1:4-5" -- 2.49.0