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Fix overbroad /proc/timer_list file permissions

PATCH New Joe Korty 2 participants 4 messages Nov 25, 2008 – Nov 26, 2008 High-resolution timers, timer wheel, clockevents

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Joe Korty

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#0 lore raw

PATCH 1/1 Fix overbroad /proc/timer_list file permissions

Fix overbroad file permissions on /proc/timer_list.

/proc/timer_list has 0644 permissions, this should be 0444.

kernel/time/timer_list.c +1 -1
Index: 2.6.28-rc6/kernel/time/timer_list.c
===================================================================
@@ -286,7 +286,7 @@
 {
 	struct proc_dir_entry *pe;
 
-	pe = proc_create("timer_list", 0644, NULL, &timer_list_fops);
+	pe = proc_create("timer_list", 0444, NULL, &timer_list_fops);
 	if (!pe)
 		return -ENOMEM;
 	return 0;
author
#1 lore raw

PATCH 1/1 Add per-cpu indexing to /proc/timer_list

Per-cpu indexing of /proc/timer_list.

/proc/timer_list, potentially a very large file, is in danger of overflowing its seq_file buffer. So 'split up' the buffering on cpu ID boundaries. This should make this file more likely to be useful on largish SMP systems.

The model followed is that in /proc/interrupts, which splits up its buffering on (most) irq boundaries.

kernel/time/timer_list.c +47 -13
Index: 2.6.28-rc6/kernel/time/timer_list.c
===================================================================
@@ -250,36 +250,70 @@
 static int timer_list_show(struct seq_file *m, void *v)
 {
 	u64 now = ktime_to_ns(ktime_get());
-	int cpu;
+	int i = *(loff_t *)v;
 
-	SEQ_printf(m, "Timer List Version: v0.4\n");
-	SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
-	SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);
-
-	for_each_online_cpu(cpu)
-		print_cpu(m, cpu, now);
-
-	SEQ_printf(m, "\n");
-	timer_list_show_tickdevices(m);
+	if (i == 0) {
+		SEQ_printf(m, "Timer List Version: v0.4\n");
+		SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n",
+			HRTIMER_MAX_CLOCK_BASES);
+		SEQ_printf(m, "now at %lld nsecs\n",
+			(unsigned long long)now);
+	}
+
+	if (i < nr_cpu_ids) {
+		if (cpu_online(i))
+			print_cpu(m, i, now);
+	}
+
+	if (i == nr_cpu_ids) {
+		SEQ_printf(m, "\n");
+		timer_list_show_tickdevices(m);
+	}
 
 	return 0;
 }
 
 void sysrq_timer_list_show(void)
 {
-	timer_list_show(NULL, NULL);
+	int i;
+	for (i = 0; i <= nr_cpu_ids; i++) {
+		loff_t v = i;
+		timer_list_show(NULL, &v);
+	}
+}
+
+static void *timer_list_start(struct seq_file *m, loff_t *pos)
+{
+	return (*pos <= nr_cpu_ids) ? pos : NULL;
 }
 
+static void *timer_list_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	if (*pos > nr_cpu_ids)
+		return NULL;
+	return pos;
+}
+
+static void timer_list_stop(struct seq_file *m, void *v) { }
+
+static const struct seq_operations timer_list_seq_ops = {
+	.start = timer_list_start,
+	.next  = timer_list_next,
+	.stop  = timer_list_stop,
+	.show  = timer_list_show
+};
+
 static int timer_list_open(struct inode *inode, struct file *filp)
 {
-	return single_open(filp, timer_list_show, NULL);
+	return seq_open(filp, &timer_list_seq_ops);
 }
 
 static struct file_operations timer_list_fops = {
 	.open		= timer_list_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= single_release,
+	.release	= seq_release,
 };
 
 static int __init init_timer_list_procfs(void)
#2 lore raw

Re: [PATCH] Add per-cpu indexing to /proc/timer_list

Quoted 6 lines · Joe Korty

Per-cpu indexing of /proc/timer_list.

/proc/timer_list, potentially a very large file, is in danger of overflowing its seq_file buffer. So 'split up' the buffering on cpu ID boundaries. This should make this file more likely to be useful on largish SMP systems.

What do you mean?

You can't overflow seq_file buffer unless kmalloc() will fail large allocation. And changing internals doesn't change amount of stuff to be shown, which is the only thing which can lead to large buffer need.

Quoted 2 lines

The model followed is that in /proc/interrupts, which splits up its buffering on (most) irq boundaries.

author
#3 lore raw

Re: [PATCH] Add per-cpu indexing to /proc/timer_list

Quoted 8 lines · Alexey Dobriyan
Quoted 6 lines · Joe Korty

Per-cpu indexing of /proc/timer_list.

/proc/timer_list, potentially a very large file, is in danger of overflowing its seq_file buffer. So 'split up' the buffering on cpu ID boundaries. This should make this file more likely to be useful on largish SMP systems.

Quoted 6 lines

What do you mean?

You can't overflow seq_file buffer unless kmalloc() will fail large allocation. And changing internals doesn't change amount of stuff to be shown, which is the only thing which can lead to large buffer need.

You're right, I missed the re-malloc part.

Joe