linux-kernel - [PATCH] serial: access-after-NULL-check-at-uart_flush

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Date:	Tue, 22 Apr 2008 12:25:52 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] serial: access-after-NULL-check-at-uart_flush_buffer

I noticed that

  static void uart_flush_buffer(struct tty_struct *tty)
  {
  	struct uart_state *state = tty->driver_data;
  	struct uart_port *port = state->port;
  	unsigned long flags;
  	
  	/*
  	 * This means you called this function _after_ the port was
  	 * closed.  No cookie for you.
  	 */
  	if (!state || !state->info) {
  		WARN_ON(1);
  		return;
  	}

is too late for checking state != NULL.
This change applies to kernels from 2.6.16 till 2.6.25.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 drivers/serial/serial_core.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletion(-)

--- linux-2.6.25.orig/drivers/serial/serial_core.c
+++ linux-2.6.25/drivers/serial/serial_core.c
@@ -535,7 +535,7 @@ static int uart_chars_in_buffer(struct t
 static void uart_flush_buffer(struct tty_struct *tty)
 {
 	struct uart_state *state = tty->driver_data;
-	struct uart_port *port = state->port;
+	struct uart_port *port;
 	unsigned long flags;
 
 	/*
@@ -547,6 +547,7 @@ static void uart_flush_buffer(struct tty
 		return;
 	}
 
+	port = state->port;
 	pr_debug("uart_flush_buffer(%d) called\n", tty->index);
 
 	spin_lock_irqsave(&port->lock, flags);
--
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