[PATCH modules-next] module: Add debugfs interface to view unloaded tainted modules

[PATCH modules-next] module: Add debugfs interface to view unloaded tainted modules

[Aaron Tomlin]

This patch provides debug/modules/unloaded_tainted file to see
a record of unloaded tainted modules.

Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
---
 kernel/module/tracking.c | 66 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/kernel/module/tracking.c b/kernel/module/tracking.c
index 7f8133044d09..015e641bc346 100644
--- a/kernel/module/tracking.c
+++ b/kernel/module/tracking.c
@@ -10,6 +10,7 @@
 #include <linux/printk.h>
 #include <linux/slab.h>
 #include <linux/list.h>
+#include <linux/debugfs.h>
 #include <linux/rculist.h>
 #include "internal.h"
 
@@ -59,3 +60,68 @@ void print_unloaded_tainted_modules(void)
 		}
 	}
 }
+
+#ifdef CONFIG_DEBUG_FS
+static void *unloaded_tainted_modules_seq_start(struct seq_file *m, loff_t *pos)
+{
+	mutex_lock(&module_mutex);
+	return seq_list_start_rcu(&unloaded_tainted_modules, *pos);
+}
+
+static void *unloaded_tainted_modules_seq_next(struct seq_file *m, void *p, loff_t *pos)
+{
+	return seq_list_next_rcu(p, &unloaded_tainted_modules, pos);
+}
+
+static void unloaded_tainted_modules_seq_stop(struct seq_file *m, void *p)
+{
+	mutex_unlock(&module_mutex);
+}
+
+static int unloaded_tainted_modules_seq_show(struct seq_file *m, void *p)
+{
+	struct mod_unload_taint *mod_taint;
+	char buf[MODULE_FLAGS_BUF_SIZE];
+	size_t l;
+
+	mod_taint = list_entry(p, struct mod_unload_taint, list);
+	l = module_flags_taint(mod_taint->taints, buf);
+	buf[l++] = '\0';
+
+	seq_printf(m, "%s (%s) %llu", mod_taint->name, buf, mod_taint->count);
+	seq_puts(m, "\n");
+
+	return 0;
+}
+
+static const struct seq_operations unloaded_tainted_modules_seq_ops = {
+	.start = unloaded_tainted_modules_seq_start,
+	.next  = unloaded_tainted_modules_seq_next,
+	.stop  = unloaded_tainted_modules_seq_stop,
+	.show  = unloaded_tainted_modules_seq_show,
+};
+
+static int unloaded_tainted_modules_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &unloaded_tainted_modules_seq_ops);
+}
+
+static const struct file_operations unloaded_tainted_modules_fops = {
+	.open = unloaded_tainted_modules_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release,
+};
+
+static int __init unloaded_tainted_modules_init(void)
+{
+	struct dentry *dir;
+
+	dir = debugfs_create_dir("modules", NULL);
+	debugfs_create_file("unloaded_tainted", 0444, dir, NULL,
+			    &unloaded_tainted_modules_fops);
+
+	return 0;
+}
+module_init(unloaded_tainted_modules_init);
+#endif /* CONFIG_DEBUG_FS */

base-commit: 554694ba120b87e39cf732ed632e6a0c52fafb7c
-- 
2.37.1

Re: [PATCH modules-next] module: Add debugfs interface to view unloaded tainted modules

[Petr Pavlu]

On 8/23/22 21:32, Aaron Tomlin wrote:
> [...]
> @@ -59,3 +60,68 @@ void print_unloaded_tainted_modules(void)
>  		}
>  	}
>  }
> +
> +#ifdef CONFIG_DEBUG_FS
> +static void *unloaded_tainted_modules_seq_start(struct seq_file *m, loff_t *pos)
> +{
> +	mutex_lock(&module_mutex);
> +	return seq_list_start_rcu(&unloaded_tainted_modules, *pos);
> +}

unloaded_tainted_modules looks to be a proper RCU list which makes me think
this reader could use just rcu_read_lock() instead of
mutex_lock(&module_mutex)?

Thanks,
Petr

Re: [PATCH modules-next] module: Add debugfs interface to view unloaded tainted modules

[Aaron Tomlin]

On Mon 2022-08-29 09:14 +0200, Petr Pavlu wrote:
> On 8/23/22 21:32, Aaron Tomlin wrote:
> > [...]
> > @@ -59,3 +60,68 @@ void print_unloaded_tainted_modules(void)
> >  		}
> >  	}
> >  }
> > +
> > +#ifdef CONFIG_DEBUG_FS
> > +static void *unloaded_tainted_modules_seq_start(struct seq_file *m, loff_t *pos)
> > +{
> > +	mutex_lock(&module_mutex);
> > +	return seq_list_start_rcu(&unloaded_tainted_modules, *pos);
> > +}

Hi Petr,

> unloaded_tainted_modules looks to be a proper RCU list which makes me think
> this reader could use just rcu_read_lock() instead of
> mutex_lock(&module_mutex)?

If I understand correctly, yes: the use of rcu_read_lock() and
rcu_read_unlock(), respectively, will be sufficient.

I will send a follow up patch.


Kind regards,

-- 
Aaron Tomlin