Commit b87324d0 authored by Catalin Marinas's avatar Catalin Marinas
Browse files

kmemleak: Do not acquire scan_mutex in kmemleak_open() 



Initially, the scan_mutex was acquired in kmemleak_open() and released
in kmemleak_release() (corresponding to /sys/kernel/debug/kmemleak
operations). This was causing some lockdep reports when the file was
closed from a different task than the one opening it. This patch moves
the scan_mutex acquiring in kmemleak_write() or kmemleak_seq_start()
with releasing in kmemleak_seq_stop().

Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 288c857d

mm/kmemleak.c

+30 −33
Original line number Diff line number Diff line
@@ -1101,6 +1101,11 @@ static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos) 
{

	struct kmemleak_object *object;

	loff_t n = *pos;

	int err;



	err = mutex_lock_interruptible(&scan_mutex);

	if (err < 0)

		return ERR_PTR(err);



	rcu_read_lock();

	list_for_each_entry_rcu(object, &object_list, object_list) {
@@ -1144,9 +1149,16 @@ static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos) 
 */

static void kmemleak_seq_stop(struct seq_file *seq, void *v)

{

	if (!IS_ERR(v)) {

		/*

		 * kmemleak_seq_start may return ERR_PTR if the scan_mutex

		 * waiting was interrupted, so only release it if !IS_ERR.

		 */

		mutex_unlock(&scan_mutex);

		if (v)

			put_object(v);

	}

}



/*

 * Print the information for an unreferenced object to the seq file.
@@ -1172,36 +1184,15 @@ static const struct seq_operations kmemleak_seq_ops = { 


static int kmemleak_open(struct inode *inode, struct file *file)

{

	int ret = 0;



	if (!atomic_read(&kmemleak_enabled))

		return -EBUSY;



	ret = mutex_lock_interruptible(&scan_mutex);

	if (ret < 0)

		goto out;

	if (file->f_mode & FMODE_READ) {

		ret = seq_open(file, &kmemleak_seq_ops);

		if (ret < 0)

			goto scan_unlock;

	}

	return ret;



scan_unlock:

	mutex_unlock(&scan_mutex);

out:

	return ret;

	return seq_open(file, &kmemleak_seq_ops);

}



static int kmemleak_release(struct inode *inode, struct file *file)

{

	int ret = 0;



	if (file->f_mode & FMODE_READ)

		seq_release(inode, file);

	mutex_unlock(&scan_mutex);



	return ret;

	return seq_release(inode, file);

}



/*
@@ -1221,15 +1212,17 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, 
{

	char buf[64];

	int buf_size;



	if (!atomic_read(&kmemleak_enabled))

		return -EBUSY;

	int ret;



	buf_size = min(size, (sizeof(buf) - 1));

	if (strncpy_from_user(buf, user_buf, buf_size) < 0)

		return -EFAULT;

	buf[buf_size] = 0;



	ret = mutex_lock_interruptible(&scan_mutex);

	if (ret < 0)

		return ret;



	if (strncmp(buf, "off", 3) == 0)

		kmemleak_disable();

	else if (strncmp(buf, "stack=on", 8) == 0)
@@ -1242,11 +1235,10 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, 
		stop_scan_thread();

	else if (strncmp(buf, "scan=", 5) == 0) {

		unsigned long secs;

		int err;



		err = strict_strtoul(buf + 5, 0, &secs);

		if (err < 0)

			return err;

		ret = strict_strtoul(buf + 5, 0, &secs);

		if (ret < 0)

			goto out;

		stop_scan_thread();

		if (secs) {

			jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
@@ -1255,7 +1247,12 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, 
	} else if (strncmp(buf, "scan", 4) == 0)

		kmemleak_scan();

	else

		return -EINVAL;

		ret = -EINVAL;



out:

	mutex_unlock(&scan_mutex);

	if (ret < 0)

		return ret;



	/* ignore the rest of the buffer, only one command at a time */

	*ppos += size;

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