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Groups > linux.kernel > #1305435

[RESEND][PATCH 15/15] tty: audit: Poison tty_audit_buf while process exits

From Peter Hurley <peter@hurleysoftware.com>
Newsgroups linux.kernel
Subject [RESEND][PATCH 15/15] tty: audit: Poison tty_audit_buf while process exits
Date 2016-01-10 06:10 +0100
Message-ID <qPgql-84a-9@gated-at.bofh.it> (permalink)
References <qPgql-84a-3@gated-at.bofh.it> <qPgql-84a-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Warn if tty_audit_buf use is attempted after tty_audit_exit() has
already freed it.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/tty_audit.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c
index fa461dc..66d53fc 100644
--- a/drivers/tty/tty_audit.c
+++ b/drivers/tty/tty_audit.c
@@ -21,6 +21,15 @@ struct tty_audit_buf {
 	unsigned char *data;	/* Allocated size N_TTY_BUF_SIZE */
 };
 
+static struct tty_audit_buf *tty_audit_buf_ref(void)
+{
+	struct tty_audit_buf *buf;
+
+	buf = current->signal->tty_audit_buf;
+	WARN_ON(buf == ERR_PTR(-ESRCH));
+	return buf;
+}
+
 static struct tty_audit_buf *tty_audit_buf_alloc(void)
 {
 	struct tty_audit_buf *buf;
@@ -106,8 +115,7 @@ void tty_audit_exit(void)
 {
 	struct tty_audit_buf *buf;
 
-	buf = current->signal->tty_audit_buf;
-	current->signal->tty_audit_buf = NULL;
+	buf = xchg(&current->signal->tty_audit_buf, ERR_PTR(-ESRCH));
 	if (!buf)
 		return;
 
@@ -158,8 +166,8 @@ int tty_audit_push(void)
 	if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
 		return -EPERM;
 
-	buf = current->signal->tty_audit_buf;
-	if (buf) {
+	buf = tty_audit_buf_ref();
+	if (!IS_ERR_OR_NULL(buf)) {
 		mutex_lock(&buf->mutex);
 		tty_audit_buf_push(buf);
 		mutex_unlock(&buf->mutex);
@@ -171,13 +179,14 @@ int tty_audit_push(void)
  *	tty_audit_buf_get	-	Get an audit buffer.
  *
  *	Get an audit buffer, allocate it if necessary.  Return %NULL
- *	if out of memory.  Otherwise, return a new reference to the buffer.
+ *	if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already
+ *	occurred.  Otherwise, return a new reference to the buffer.
  */
 static struct tty_audit_buf *tty_audit_buf_get(void)
 {
 	struct tty_audit_buf *buf;
 
-	buf = current->signal->tty_audit_buf;
+	buf = tty_audit_buf_ref();
 	if (buf)
 		return buf;
 
@@ -190,7 +199,7 @@ static struct tty_audit_buf *tty_audit_buf_get(void)
 	/* Race to use this buffer, free it if another wins */
 	if (cmpxchg(&current->signal->tty_audit_buf, NULL, buf) != NULL)
 		tty_audit_buf_free(buf);
-	return current->signal->tty_audit_buf;
+	return tty_audit_buf_ref();
 }
 
 /**
@@ -220,7 +229,7 @@ void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
 		return;
 
 	buf = tty_audit_buf_get();
-	if (!buf)
+	if (IS_ERR_OR_NULL(buf))
 		return;
 
 	mutex_lock(&buf->mutex);
-- 
2.7.0

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Thread

[RESEND][PATCH 00/15] Rework tty audit Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 11/15] tty: audit: Remove tty_audit_buf reference counting Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 15/15] tty: audit: Poison tty_audit_buf while process exits Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 02/15] tty: audit: Never audit packet mode Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 03/15] tty: audit: Remove icanon mode from call chain Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 09/15] tty: audit: Handle tty audit enable atomically Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 04/15] tty: audit: Defer audit buffer association Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 06/15] tty: audit: Ignore current association for audit push Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
    Re: [RESEND][PATCH 06/15] tty: audit: Ignore current association for  audit push kbuild test robot <lkp@intel.com> - 2016-01-10 06:40 +0100
      Re: [RESEND][PATCH 06/15] tty: audit: Ignore current association for  audit push Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:10 +0100
  [RESEND][PATCH 14/15] tty: audit: Always push audit buffer before TIOCSTI Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 05/15] tty: audit: Take siglock directly Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 13/15] tty: audit: Check audit enable first Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 12/15] tty: audit: Simplify first-use allocation Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 01/15] tty: audit: Early-out pty master reads earlier Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 08/15] tty: audit: Track tty association with dev_t Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 07/15] tty: audit: Combine push functions Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [RESEND][PATCH 10/15] tty: audit: Remove false memory optimization Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:10 +0100
  [PATCH v2 12/15] tty: audit: Simplify first-use allocation Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
  [PATCH v2 11/15] tty: audit: Remove tty_audit_buf reference counting Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
  [PATCH v2 00/15] Rework tty audit Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 02/15] tty: audit: Never audit packet mode Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 15/15] tty: audit: Poison tty_audit_buf while process exits Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 10/15] tty: audit: Remove false memory optimization Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 09/15] tty: audit: Handle tty audit enable atomically Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 14/15] tty: audit: Always push audit buffer before TIOCSTI Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 13/15] tty: audit: Check audit enable first Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 01/15] tty: audit: Early-out pty master reads earlier Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 08/15] tty: audit: Track tty association with dev_t Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:00 +0100
    [PATCH v2 04/15] tty: audit: Defer audit buffer association Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:10 +0100
    [PATCH v2 03/15] tty: audit: Remove icanon mode from call chain Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:10 +0100
    [PATCH v2 05/15] tty: audit: Take siglock directly Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:10 +0100
    [PATCH v2 07/15] tty: audit: Combine push functions Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:10 +0100
    [PATCH v2 06/15] tty: audit: Ignore current association for audit push Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 08:10 +0100

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