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: [email protected]
Signed-off-by: Hui Peng <[email protected]>
---
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
