From 1cc77248106aafc12ba529953f652d6f8db2c84d Mon Sep 17 00:00:00 2001 From: Chuck Ebbert <76306.1226@compuserve.com> Date: Fri, 19 Aug 2005 14:14:07 +0200 Subject: [WATCHDOG] softdog-timer-running-oops.patch The softdog watchdog timer has a bug that can create an oops: 1. Load the module without the nowayout option. 2. Open the driver and close it without writing 'V' before close. 3. Unload the module. The timer will continue to run... 4. Oops happens when timer fires. Reported Sun, 10 Oct 2004, by Michael Schierl Fix is easy: always take a reference on the module on open. Release it only when the device is closed and no timer is running. Tested on 2.6.13-rc6 using the soft_noboot option. While the timer is running and the device is closed, the module use count stays at 1. After the timer fires, it drops to 0. Repeatedly opening and closing the driver caused no problems. Please apply. Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Wim Van Sebroeck --- drivers/char/watchdog/softdog.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'drivers') diff --git a/drivers/char/watchdog/softdog.c b/drivers/char/watchdog/softdog.c index 4d7ed931f5c6..20e5eb8667f2 100644 --- a/drivers/char/watchdog/softdog.c +++ b/drivers/char/watchdog/softdog.c @@ -77,7 +77,7 @@ static void watchdog_fire(unsigned long); static struct timer_list watchdog_ticktock = TIMER_INITIALIZER(watchdog_fire, 0, 0); -static unsigned long timer_alive; +static unsigned long driver_open, orphan_timer; static char expect_close; @@ -87,6 +87,9 @@ static char expect_close; static void watchdog_fire(unsigned long data) { + if (test_and_clear_bit(0, &orphan_timer)) + module_put(THIS_MODULE); + if (soft_noboot) printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n"); else @@ -128,9 +131,9 @@ static int softdog_set_heartbeat(int t) static int softdog_open(struct inode *inode, struct file *file) { - if(test_and_set_bit(0, &timer_alive)) + if (test_and_set_bit(0, &driver_open)) return -EBUSY; - if (nowayout) + if (!test_and_clear_bit(0, &orphan_timer)) __module_get(THIS_MODULE); /* * Activate timer @@ -147,11 +150,13 @@ static int softdog_release(struct inode *inode, struct file *file) */ if (expect_close == 42) { softdog_stop(); + module_put(THIS_MODULE); } else { printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n"); + set_bit(0, &orphan_timer); softdog_keepalive(); } - clear_bit(0, &timer_alive); + clear_bit(0, &driver_open); expect_close = 0; return 0; } -- cgit v1.2.3