Breno reported a kmemleak for sd->shared assignment on an asymmetric
system with a single LLC.

Post the unconditional assignment of sd->shared for sd_llc in commit
9e005ed21152d ("sched/topology: Allow multiple domains to claim
sched_domain_shared"), init_sched_domain_shared() can overrwrite the
sd->shared assignment for as_asym_cpucapacity when sd_llc and
as_asym_cpucapacity point to the same domain.

Return early from init_sched_domain_shared() if a valid sd->shared
assignment is detected. Since the degeneration path only decrements the
refcount by 1, it is correct to only account the sd->shared assignment
once per sched-domain level, even if the flags overlap.

While at it, correct a typo in init_sched_domain_shared().

Reported-by: Breno Leitao <leitao@debian.org>
Closes: https://lore.kernel.org/lkml/akeMbyZGmbjWSZqp@gmail.com/
Fixes: 9e005ed21152d ("sched/topology: Allow multiple domains to claim sched_domain_shared")
Tested-by: Breno Leitao <leitao@debian.org>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
---
 kernel/sched/topology.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 622e2e01974c4..b761ecda790a8 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2942,6 +2942,14 @@ init_sched_domain_shared(struct s_data *d, struct sched_domain *sd, int flags)
 	struct sched_domain_shared *sds = NULL;
 	int cpu;
 
+	/*
+	 * sd->shared is already assigned for this domain level for a
+	 * different flag. Nothing to do since this allocation is
+	 * already accounted for.
+	 */
+	if (sd->shared)
+		return;
+
 	/*
 	 * Multiple domains can try to claim a shared object like
 	 * SD_ASYM_CPUCAPACITY and SD_SHARE_LLC which can alias to
@@ -2970,7 +2978,7 @@ init_sched_domain_shared(struct s_data *d, struct sched_domain *sd, int flags)
 
 	/*
 	 * Use the sd_shared corresponding to the last
-	 * CPU in the span if none are avaialable.
+	 * CPU in the span if none are available.
 	 */
 	if (WARN_ON_ONCE(!sd->shared))
 		sd->shared = sds;

base-commit: 04998aa54848f15332202d0bea008d2ca1ed1713
-- 
2.34.1