linux-kernel - [PATCH v1] tty: serial: 8250: Fix possible race in serial8250_em485

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 11 Feb 2016 22:32:32 +0300
From:	"Matwey V. Kornilov" <matwey@....msu.ru>
To:	gregkh@...uxfoundation.org, jslaby@...e.com,
	peter@...leysoftware.com, andy.shevchenko@...il.com,
	gnomes@...rguk.ukuu.org.uk
Cc:	"Matwey V. Kornilov" <matwey@....msu.ru>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: [PATCH v1] tty: serial: 8250: Fix possible race in serial8250_em485_destroy()

Fix possbile race in serial8250_em485_destroy() when timer handlers can
dereference p->em485 which is alread destroyed but not yet NULLed.

Signed-off-by: Matwey V. Kornilov <matwey@....msu.ru>
---
I've found that Greg applied initial patchset, so this erratum goes as separate patch.

 drivers/tty/serial/8250/8250_port.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index c908b77..d962de2 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -617,14 +617,16 @@ EXPORT_SYMBOL_GPL(serial8250_em485_init);
  */
 void serial8250_em485_destroy(struct uart_8250_port *p)
 {
-	if (p->em485 == NULL)
+	struct uart_8250_em485 *em485 = p->em485;
+
+	if (!em485)
 		return;
 
-	del_timer(&p->em485->start_tx_timer);
-	del_timer(&p->em485->stop_tx_timer);
+	del_timer(&em485->start_tx_timer);
+	del_timer(&em485->stop_tx_timer);
 
-	kfree(p->em485);
 	p->em485 = NULL;
+	kfree(em485);
 }
 EXPORT_SYMBOL_GPL(serial8250_em485_destroy);
 
-- 
2.7.0