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Message-Id: <20230819141239.287290-4-yury.norov@gmail.com>
Date: Sat, 19 Aug 2023 07:12:35 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: Yury Norov <yury.norov@...il.com>, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ben Segall <bsegall@...gle.com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Jacob Keller <jacob.e.keller@...el.com>,
Jakub Kicinski <kuba@...nel.org>,
Juri Lelli <juri.lelli@...hat.com>,
Mel Gorman <mgorman@...e.de>,
Steven Rostedt <rostedt@...dmis.org>,
Tariq Toukan <tariqt@...dia.com>,
Valentin Schneider <vschneid@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
shiju.jose@...wei.com, jonathan.cameron@...wei.com,
prime.zeng@...wei.com, linuxarm@...wei.com,
yangyicong@...ilicon.com,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH v2 3/6] sched: fix sched_numa_find_nth_cpu() in CPU-less case
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@...ilicon.com>
Closes: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/
Reported-by: Guenter Roeck <linux@...ck-us.net>
Closes: https://lore.kernel.org/lkml/ZMHSNQfv39HN068m@yury-ThinkPad/T/#mf6431cb0b7f6f05193c41adeee444bc95bf2b1c4
Signed-off-by: Yury Norov <yury.norov@...il.com>
Reviewed-by: Yicong Yang <yangyicong@...ilicon.com>
---
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..c6e89afa0d65 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;
--
2.39.2
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