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Commit 5493090f authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: audit: Remove tty_audit_buf reference counting 



When tty_audit_exit() is called from do_exit(), the process is
single-threaded. Since the tty_audit_buf is only shared by threads
of a process, no other thread can be concurrently accessing the
tty_audit_buf during or after tty_audit_exit().

Thus, no other thread can be holding an extra tty_audit_buf reference
which would prevent tty_audit_exit() from freeing the tty_audit_buf.
As that is the only purpose of the ref counting, remove the reference
counting and free the tty_audit_buf directly.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5c8b3185

drivers/tty/tty_audit.c

+7 −40
Original line number Diff line number Diff line
@@ -14,7 +14,6 @@ 
#include <linux/tty.h>



struct tty_audit_buf {

	atomic_t count;

	struct mutex mutex;	/* Protects all data below */

	dev_t dev;		/* The TTY which the data is from */

	unsigned icanon:1;
@@ -32,7 +31,6 @@ static struct tty_audit_buf *tty_audit_buf_alloc(void) 
	buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);

	if (!buf->data)

		goto err_buf;

	atomic_set(&buf->count, 1);

	mutex_init(&buf->mutex);

	buf->dev = MKDEV(0, 0);

	buf->icanon = 0;
@@ -52,12 +50,6 @@ static void tty_audit_buf_free(struct tty_audit_buf *buf) 
	kfree(buf);

}



static void tty_audit_buf_put(struct tty_audit_buf *buf)

{

	if (atomic_dec_and_test(&buf->count))

		tty_audit_buf_free(buf);

}



static void tty_audit_log(const char *description, dev_t dev,

			  unsigned char *data, size_t size)

{
@@ -106,6 +98,9 @@ static void tty_audit_buf_push(struct tty_audit_buf *buf) 
 *

 *	Make sure all buffered data is written out and deallocate the buffer.

 *	Only needs to be called if current->signal->tty_audit_buf != %NULL.

 *

 *	The process is single-threaded at this point; no other threads share

 *	current->signal.

 */

void tty_audit_exit(void)

{
@@ -116,11 +111,8 @@ void tty_audit_exit(void) 
	if (!buf)

		return;



	mutex_lock(&buf->mutex);

	tty_audit_buf_push(buf);

	mutex_unlock(&buf->mutex);



	tty_audit_buf_put(buf);

	tty_audit_buf_free(buf);

}



/**
@@ -140,21 +132,14 @@ void tty_audit_tiocsti(struct tty_struct *tty, char ch) 
{

	struct tty_audit_buf *buf;

	dev_t dev;

	unsigned long flags;



	spin_lock_irqsave(&current->sighand->siglock, flags);

	buf = current->signal->tty_audit_buf;

	if (buf)

		atomic_inc(&buf->count);

	spin_unlock_irqrestore(&current->sighand->siglock, flags);



	dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;

	buf = current->signal->tty_audit_buf;

	if (buf) {

		mutex_lock(&buf->mutex);

		if (buf->dev == dev)

			tty_audit_buf_push(buf);

		mutex_unlock(&buf->mutex);

		tty_audit_buf_put(buf);

	}



	if (audit_enabled && (current->signal->audit_tty & AUDIT_TTY_ENABLE)) {
@@ -175,23 +160,15 @@ void tty_audit_tiocsti(struct tty_struct *tty, char ch) 
int tty_audit_push(void)

{

	struct tty_audit_buf *buf;

	unsigned long flags;



	if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)

		return -EPERM;



	spin_lock_irqsave(&current->sighand->siglock, flags);

	buf = current->signal->tty_audit_buf;

	if (buf)

		atomic_inc(&buf->count);

	spin_unlock_irqrestore(&current->sighand->siglock, flags);



	if (buf) {

		mutex_lock(&buf->mutex);

		tty_audit_buf_push(buf);

		mutex_unlock(&buf->mutex);



		tty_audit_buf_put(buf);

	}

	return 0;

}
@@ -207,15 +184,9 @@ static struct tty_audit_buf *tty_audit_buf_get(void) 
	struct tty_audit_buf *buf, *buf2;

	unsigned long flags;



	buf = NULL;

	buf2 = NULL;

	spin_lock_irqsave(&current->sighand->siglock, flags);

	buf = current->signal->tty_audit_buf;

	if (buf) {

		atomic_inc(&buf->count);

		goto out;

	}

	spin_unlock_irqrestore(&current->sighand->siglock, flags);

	if (buf)

		return buf;



	buf2 = tty_audit_buf_alloc();

	if (buf2 == NULL) {
@@ -230,9 +201,6 @@ static struct tty_audit_buf *tty_audit_buf_get(void) 
		buf = buf2;

		buf2 = NULL;

	}

	atomic_inc(&buf->count);

	/* Fall through */

 out:

	spin_unlock_irqrestore(&current->sighand->siglock, flags);

	if (buf2)

		tty_audit_buf_free(buf2);
@@ -289,5 +257,4 @@ void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size) 
			tty_audit_buf_push(buf);

	} while (size != 0);

	mutex_unlock(&buf->mutex);

	tty_audit_buf_put(buf);

}