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Thu, 10 Aug 2023 09:24:56 -0700 (PDT) From: Yury Norov To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Yury Norov , Ingo Molnar , Peter Zijlstra , Andrew Morton , Ben Segall , Daniel Bristot de Oliveira , Dietmar Eggemann , Jacob Keller , Jakub Kicinski , Juri Lelli , Mel Gorman , Peter Lafreniere , Steven Rostedt , Tariq Toukan , Valentin Schneider , Vincent Guittot , shiju.jose@huawei.com, jonathan.cameron@huawei.com, prime.zeng@huawei.com, linuxarm@huawei.com, yangyicong@hisilicon.com, Andy Shevchenko , Rasmus Villemoes , Guenter Roeck Subject: [PATCH 3/4] sched: fix sched_numa_find_nth_cpu() in CPU-less case Date: Thu, 10 Aug 2023 09:24:41 -0700 Message-Id: <20230810162442.9863-4-yury.norov@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230810162442.9863-1-yury.norov@gmail.com> References: <20230810162442.9863-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: A843A4000B X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 6ib1buawdu97xey4wtn14dgir43upzs4 X-HE-Tag: 1691684697-149982 X-HE-Meta: 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 BdJLy6PS 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Closes: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/ Reported-by: Guenter Roeck Closes: https://lore.kernel.org/lkml/ZMHSNQfv39HN068m@yury-ThinkPad/T/#mf6431cb0b7f6f05193c41adeee444bc95bf2b1c4 Signed-off-by: Yury Norov --- This has been discovered and fixed by Yicong Yang: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/ When discovering Guenter's failure report for sparc64, I found it's due to the same problem. And while fixing, I found an opportunity to generalize nearest NUMA node search and avoid code duplication. Yicong, if you like this approach, please feel free to add your co-developed-by or any appropriate tags. 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 d3a3b2646ec4..66b387172b6f 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2113,10 +2113,14 @@ 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; + /* CPU-less node entries are uninitialized in sched_domains_numa_masks */ + node = numa_nearest_node(node, N_CPU); + k.node = node; + rcu_read_lock(); k.masks = rcu_dereference(sched_domains_numa_masks); -- 2.39.2