6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Yury Norov yury.norov@gmail.com
[ Upstream commit 617f2c38cb5ce60226042081c09e2ee3a90d03f8 ]
When the node provided by user is CPU-less, corresponding record in sched_domains_numa_masks is not set. Trying to dereference it in the following code leads to kernel crash.
To avoid it, start searching from the nearest node with CPUs.
Fixes: cd7f55359c90 ("sched: add sched_numa_find_nth_cpu()") Reported-by: Yicong Yang yangyicong@hisilicon.com Reported-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Yury Norov yury.norov@gmail.com Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Yicong Yang yangyicong@hisilicon.com Cc: Mel Gorman mgorman@suse.de Link: https://lore.kernel.org/r/20230819141239.287290-4-yury.norov@gmail.com
Closes: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO... Closes: https://lore.kernel.org/lkml/ZMHSNQfv39HN068m@yury-ThinkPad/T/#mf6431cb0b7f6... Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/topology.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d3a3b2646ec4f..c6e89afa0d65c 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2113,12 +2113,16 @@ static int hop_cmp(const void *a, const void *b) */ int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node) { - struct __cmp_key k = { .cpus = cpus, .node = node, .cpu = cpu }; + struct __cmp_key k = { .cpus = cpus, .cpu = cpu }; struct cpumask ***hop_masks; int hop, ret = nr_cpu_ids;
rcu_read_lock();
+ /* CPU-less node entries are uninitialized in sched_domains_numa_masks */ + node = numa_nearest_node(node, N_CPU); + k.node = node; + k.masks = rcu_dereference(sched_domains_numa_masks); if (!k.masks) goto unlock;