genirq/proc: Correctly set file permissions for affinity control files

The kernel already knows at the time of interrupt allocation whether
affinity of an interrupt can be controlled by userspace or not.

It still creates all related procfs control files with read/write
permissions. That's inconsistent and non-intuitive for system
administrators and tools.

Therefore set the file permissions to read-only for such interrupts.

[ tglx: Massage change log, fixed UP build ]

Signed-off-by: Jeff Xie <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

Author: Jeff Xie

kernel/irq/proc.c

@@ -362,16 +362,21 @@ void register_irq_proc(unsigned int irq, struct irq_desc *desc)
 		goto out_unlock;
 
 #ifdef CONFIG_SMP
+	umode_t umode = S_IRUGO;
+
+	if (irq_can_set_affinity_usr(desc->irq_data.irq))
+		umode |= S_IWUSR;
+
 	/* create /proc/irq/<irq>/smp_affinity */
-	proc_create_data("smp_affinity", 0644, desc->dir,
+	proc_create_data("smp_affinity", umode, desc->dir,
 			 &irq_affinity_proc_ops, irqp);
 
 	/* create /proc/irq/<irq>/affinity_hint */
 	proc_create_single_data("affinity_hint", 0444, desc->dir,
 			irq_affinity_hint_proc_show, irqp);
 
 	/* create /proc/irq/<irq>/smp_affinity_list */
-	proc_create_data("smp_affinity_list", 0644, desc->dir,
+	proc_create_data("smp_affinity_list", umode, desc->dir,
 			 &irq_affinity_list_proc_ops, irqp);
 
 	proc_create_single_data("node", 0444, desc->dir, irq_node_proc_show,