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tty: audit: Handle tty audit enable atomically 

The audit_tty and audit_tty_log_passwd fields are actually bool
values, so merge into single memory location to access atomically.

NB: audit log operations may still occur after tty audit is disabled
which is consistent with the existing functionality

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Peter Hurley 2016-01-09 22:55:33 -08:00 committed by Greg Kroah-Hartman
parent 4d240b6442
commit 2e28d38ae1
4 changed files with 38 additions and 45 deletions
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53
drivers/tty/tty_audit.c
View File

@ -131,7 +131,6 @@ void tty_audit_exit(void)
void tty_audit_fork(struct signal_struct *sig)
{
sig->audit_tty = current->signal->audit_tty;
sig->audit_tty_log_passwd = current->signal->audit_tty_log_passwd;
}
/**
@ -141,11 +140,9 @@ void tty_audit_tiocsti(struct tty_struct *tty, char ch)
{
struct tty_audit_buf *buf;
dev_t dev;
int should_audit;
unsigned long flags;
spin_lock_irqsave(&current->sighand->siglock, flags);
should_audit = current->signal->audit_tty;
buf = current->signal->tty_audit_buf;
if (buf)
atomic_inc(&buf->count);
@ -160,7 +157,7 @@ void tty_audit_tiocsti(struct tty_struct *tty, char ch)
tty_audit_buf_put(buf);
}
if (should_audit && audit_enabled) {
if (audit_enabled && (current->signal->audit_tty & AUDIT_TTY_ENABLE)) {
kuid_t auid;
unsigned int sessionid;
@ -177,29 +174,25 @@ void tty_audit_tiocsti(struct tty_struct *tty, char ch)
*/
int tty_audit_push(void)
{
struct tty_audit_buf *buf = ERR_PTR(-EPERM);
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);
if (current->signal->audit_tty) {
buf = current->signal->tty_audit_buf;
if (buf)
atomic_inc(&buf->count);
}
buf = current->signal->tty_audit_buf;
if (buf)
atomic_inc(&buf->count);
spin_unlock_irqrestore(&current->sighand->siglock, flags);
/*
* Return 0 when signal->audit_tty set
* but current->signal->tty_audit_buf == NULL.
*/
if (!buf || IS_ERR(buf))
return PTR_ERR(buf);
if (buf) {
mutex_lock(&buf->mutex);
tty_audit_buf_push(buf);
mutex_unlock(&buf->mutex);
mutex_lock(&buf->mutex);
tty_audit_buf_push(buf);
mutex_unlock(&buf->mutex);
tty_audit_buf_put(buf);
tty_audit_buf_put(buf);
}
return 0;
}
@ -218,8 +211,6 @@ static struct tty_audit_buf *tty_audit_buf_get(void)
buf = NULL;
buf2 = NULL;
spin_lock_irqsave(&current->sighand->siglock, flags);
if (likely(!current->signal->audit_tty))
goto out;
buf = current->signal->tty_audit_buf;
if (buf) {
atomic_inc(&buf->count);
@ -233,9 +224,10 @@ static struct tty_audit_buf *tty_audit_buf_get(void)
return NULL;
}
spin_lock_irqsave(&current->sighand->siglock, flags);
if (!current->signal->audit_tty)
if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
goto out;
spin_lock_irqsave(&current->sighand->siglock, flags);
buf = current->signal->tty_audit_buf;
if (!buf) {
current->signal->tty_audit_buf = buf2;
@ -259,9 +251,8 @@ static struct tty_audit_buf *tty_audit_buf_get(void)
void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
{
struct tty_audit_buf *buf;
int audit_log_tty_passwd;
unsigned long flags;
unsigned int icanon = !!L_ICANON(tty);
unsigned int audit_tty;
dev_t dev;
if (unlikely(size == 0))
@ -271,10 +262,10 @@ void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
&& tty->driver->subtype == PTY_TYPE_MASTER)
return;
spin_lock_irqsave(&current->sighand->siglock, flags);
audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
spin_unlock_irqrestore(&current->sighand->siglock, flags);
if (!audit_log_tty_passwd && icanon && !L_ECHO(tty))
audit_tty = READ_ONCE(current->signal->audit_tty);
if (~audit_tty & AUDIT_TTY_ENABLE)
return;
if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
return;
buf = tty_audit_buf_get();

4
include/linux/audit.h
View File

@ -109,6 +109,10 @@ extern int audit_classify_compat_syscall(int abi, unsigned syscall);
/* maximized args number that audit_socketcall can process */
#define AUDITSC_ARGS 6
/* bit values for ->signal->audit_tty */
#define AUDIT_TTY_ENABLE BIT(0)
#define AUDIT_TTY_LOG_PASSWD BIT(1)
struct filename;
extern void audit_log_session_info(struct audit_buffer *ab);

1
include/linux/sched.h
View File

@ -775,7 +775,6 @@ struct signal_struct {
#endif
#ifdef CONFIG_AUDIT
unsigned audit_tty;
unsigned audit_tty_log_passwd;
struct tty_audit_buf *tty_audit_buf;
#endif

25
kernel/audit.c
View File

@ -1030,20 +1030,19 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
break;
case AUDIT_TTY_GET: {
struct audit_tty_status s;
struct task_struct *tsk = current;
unsigned int t;
spin_lock(&tsk->sighand->siglock);
s.enabled = tsk->signal->audit_tty;
s.log_passwd = tsk->signal->audit_tty_log_passwd;
spin_unlock(&tsk->sighand->siglock);
t = READ_ONCE(current->signal->audit_tty);
s.enabled = t & AUDIT_TTY_ENABLE;
s.log_passwd = !!(t & AUDIT_TTY_LOG_PASSWD);
audit_send_reply(skb, seq, AUDIT_TTY_GET, 0, 0, &s, sizeof(s));
break;
}
case AUDIT_TTY_SET: {
struct audit_tty_status s, old;
struct task_struct *tsk = current;
struct audit_buffer *ab;
unsigned int t;
memset(&s, 0, sizeof(s));
/* guard against past and future API changes */
@ -1053,14 +1052,14 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
(s.log_passwd != 0 && s.log_passwd != 1))
err = -EINVAL;
spin_lock(&tsk->sighand->siglock);
old.enabled = tsk->signal->audit_tty;
old.log_passwd = tsk->signal->audit_tty_log_passwd;
if (!err) {
tsk->signal->audit_tty = s.enabled;
tsk->signal->audit_tty_log_passwd = s.log_passwd;
if (err)
t = READ_ONCE(current->signal->audit_tty);
else {
t = s.enabled | (-s.log_passwd & AUDIT_TTY_LOG_PASSWD);
t = xchg(&current->signal->audit_tty, t);
}
spin_unlock(&tsk->sighand->siglock);
old.enabled = t & AUDIT_TTY_ENABLE;
old.log_passwd = !!(t & AUDIT_TTY_LOG_PASSWD);
audit_log_common_recv_msg(&ab, AUDIT_CONFIG_CHANGE);
audit_log_format(ab, " op=tty_set old-enabled=%d new-enabled=%d"