kthread: Fix return value on kzalloc() failure in kthread_affine_preferred()

kthread_affine_preferred() incorrectly returns 0 instead of -ENOMEM
when kzalloc() fails. Return 'ret' to ensure the correct error code is
propagated.

Fixes: 4d13f43 ("kthread: Implement preferred affinity")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501301528.t0cZVbnq-lkp@intel.com/
Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Author: eleanorLYJ

kernel/kthread.c

@@ -859,7 +859,7 @@ int kthread_affine_preferred(struct task_struct *p, const struct cpumask *mask)
 	struct kthread *kthread = to_kthread(p);
 	cpumask_var_t affinity;
 	unsigned long flags;
-	int ret;
+	int ret = 0;
 
 	if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE) || kthread->started) {
 		WARN_ON(1);
@@ -892,7 +892,7 @@ int kthread_affine_preferred(struct task_struct *p, const struct cpumask *mask)
 out:
 	free_cpumask_var(affinity);
 
-	return 0;
+	return ret;
 }
 
 /*