From 5657c116783545fb49cd7004994c187128552b12 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Sun, 15 Jan 2023 14:31:22 -0500 Subject: sched/core: Fix NULL pointer access fault in sched_setaffinity() with non-SMP configs The kernel commit 9a5418bc48ba ("sched/core: Use kfree_rcu() in do_set_cpus_allowed()") introduces a bug for kernels built with non-SMP configs. Calling sched_setaffinity() on such a uniprocessor kernel will cause cpumask_copy() to be called with a NULL pointer leading to general protection fault. This is not really a problem in real use cases as there aren't that many uniprocessor kernel configs in use and calling sched_setaffinity() on such a uniprocessor system doesn't make sense. Fix this problem by making sure cpumask_copy() will not be called in such a case. Fixes: 9a5418bc48ba ("sched/core: Use kfree_rcu() in do_set_cpus_allowed()") Reported-by: kernel test robot Signed-off-by: Waiman Long Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/20230115193122.563036-1-longman@redhat.com --- kernel/sched/core.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'kernel/sched') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index bb1ee6d7bdde..e838feb6adc5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8290,12 +8290,18 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask) if (retval) goto out_put_task; + /* + * With non-SMP configs, user_cpus_ptr/user_mask isn't used and + * alloc_user_cpus_ptr() returns NULL. + */ user_mask = alloc_user_cpus_ptr(NUMA_NO_NODE); - if (IS_ENABLED(CONFIG_SMP) && !user_mask) { + if (user_mask) { + cpumask_copy(user_mask, in_mask); + } else if (IS_ENABLED(CONFIG_SMP)) { retval = -ENOMEM; goto out_put_task; } - cpumask_copy(user_mask, in_mask); + ac = (struct affinity_context){ .new_mask = in_mask, .user_mask = user_mask, -- cgit v1.2.3