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SubjectRe: [patch 2.6.13-rc6] watchdog: fix oops in softdog driver
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On Iau, 2005-08-18 at 01:09 -0400, Chuck Ebbert wrote:
> Wim,
> 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 <schierlm@gmx.de>
>
> 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>
>
> drivers/char/watchdog/softdog.c | 13 +++++++++----
> 1 files changed, 9 insertions(+), 4 deletions(-)
>
> --- 2.6.13-rc6c.orig/drivers/char/watchdog/softdog.c
> +++ 2.6.13-rc6c/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
> */
> 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;
> }
> __
> Chuck
-
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