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Commit b50819f4 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

tty: audit: Ignore current association for audit push 



In canonical read mode, each line read and logged is pushed separately
with tty_audit_push(). For all single-threaded processes and multi-threaded
processes reading from only one tty, this patch has no effect; the last line
read will still be the entry pushed to the audit log because the tty
association cannot have changed between tty_audit_add_data() and
tty_audit_push().

For multi-threaded processes reading from different ttys concurrently,
the audit log will have mixed log entries anyway. Consider two ttys
audited concurrently:

CPU0                           CPU1
----------                     ------------
tty_audit_add_data(ttyA)
                               tty_audit_add_data(ttyB)
tty_audit_push()
                               tty_audit_add_data(ttyB)
                               tty_audit_push()

This patch will now cause the ttyB output to be split into separate
audit log entries.

However, this possibility is equally likely without this patch:

CPU0                           CPU1
----------                     ------------
                               tty_audit_add_data(ttyB)
tty_audit_add_data(ttyA)
tty_audit_push()
                               tty_audit_add_data(ttyB)
                               tty_audit_push()

Mixed canonical and non-canonical reads have similar races.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f229c2c1

drivers/tty/n_tty.c

+1 −1
Original line number Diff line number Diff line
@@ -2072,7 +2072,7 @@ static int canon_copy_from_read_buf(struct tty_struct *tty, 
			ldata->line_start = ldata->read_tail;

		else

			ldata->push = 0;

		tty_audit_push(tty);

		tty_audit_push();

	}

	return 0;

}

drivers/tty/tty_audit.c

+3 −8
Original line number Diff line number Diff line
@@ -313,9 +313,9 @@ void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size) 
/**

 *	tty_audit_push	-	Push buffered data out

 *

 *	Make sure no audit data is pending for @tty on the current process.

 *	Make sure no audit data is pending on the current process.

 */

void tty_audit_push(struct tty_struct *tty)

void tty_audit_push(void)

{

	struct tty_audit_buf *buf;

	unsigned long flags;
@@ -331,12 +331,7 @@ void tty_audit_push(struct tty_struct *tty) 
	spin_unlock_irqrestore(&current->sighand->siglock, flags);



	if (buf) {

		int major, minor;



		major = tty->driver->major;

		minor = tty->driver->minor_start + tty->index;

		mutex_lock(&buf->mutex);

		if (buf->major == major && buf->minor == minor)

		tty_audit_buf_push(buf);

		mutex_unlock(&buf->mutex);

		tty_audit_buf_put(buf);

include/linux/tty.h

+2 −2
Original line number Diff line number Diff line
@@ -597,7 +597,7 @@ extern void tty_audit_add_data(struct tty_struct *tty, const void *data, 
extern void tty_audit_exit(void);

extern void tty_audit_fork(struct signal_struct *sig);

extern void tty_audit_tiocsti(struct tty_struct *tty, char ch);

extern void tty_audit_push(struct tty_struct *tty);

extern void tty_audit_push(void);

extern int tty_audit_push_current(void);

#else

static inline void tty_audit_add_data(struct tty_struct *tty, const void *data,
@@ -613,7 +613,7 @@ static inline void tty_audit_exit(void) 
static inline void tty_audit_fork(struct signal_struct *sig)

{

}

static inline void tty_audit_push(struct tty_struct *tty)

static inline void tty_audit_push(void)

{

}

static inline int tty_audit_push_current(void)