[RESEND][PATCH 09/15] tty: audit: Handle tty audit enable atomically
Peter Hurley
peter at hurleysoftware.com
Sun Jan 10 04:59:02 UTC 2016
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 at hurleysoftware.com>
---
drivers/tty/tty_audit.c | 53 ++++++++++++++++++++-----------------------------
include/linux/audit.h | 4 ++++
include/linux/sched.h | 1 -
kernel/audit.c | 25 +++++++++++------------
4 files changed, 38 insertions(+), 45 deletions(-)
diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c
index 50380d8..3d90f88 100644
--- a/drivers/tty/tty_audit.c
+++ b/drivers/tty/tty_audit.c
@@ -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(¤t->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(¤t->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(¤t->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);
-
- mutex_lock(&buf->mutex);
- tty_audit_buf_push(buf);
- mutex_unlock(&buf->mutex);
+ if (buf) {
+ 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(¤t->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(¤t->sighand->siglock, flags);
- if (!current->signal->audit_tty)
+ if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
goto out;
+
+ spin_lock_irqsave(¤t->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(¤t->sighand->siglock, flags);
- audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
- spin_unlock_irqrestore(¤t->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();
diff --git a/include/linux/audit.h b/include/linux/audit.h
index 20eba1e..9ed7254 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -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);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index edad7a4..400a738 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -771,7 +771,6 @@ struct signal_struct {
#endif
#ifdef CONFIG_AUDIT
unsigned audit_tty;
- unsigned audit_tty_log_passwd;
struct tty_audit_buf *tty_audit_buf;
#endif
diff --git a/kernel/audit.c b/kernel/audit.c
index 270dfb9..dfaa8e7 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1031,20 +1031,19 @@ 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 */
@@ -1054,14 +1053,14 @@ 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(¤t->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"
--
2.7.0
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