On 9/24/26 12:27 AM, Hui Peng wrote:
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: [email protected]
Assisted-by: LLM
Signed-off-by: Hui Peng <[email protected]>
---
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;
The code change looks good to me.
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"
This test case is problematic as it fails on my test system because of a
bug in the SCHED_DEADLINE task shrink test in validate_change() that can
be triggered if there are deadline tasks in the system which will fail
the test. I am going to post a patch to fix that bug. Can you take out
this test case from this patch as I don't want this test to be
backported to stable releases? You can send this out as a separate
testing patch if you want to.
Cheers,
Longman
# Local partition invalidation tests
" C0-3:X1-3:P2 C1-3:X2-3:P2 C2-3:X3:P2 \
