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Wed, 23 Jun 2021 04:31:48 -0700 (PDT) Sender: Guenter Roeck Date: Wed, 23 Jun 2021 04:31:46 -0700 From: Guenter Roeck To: Curtis Klein Cc: wim@linux-watchdog.org, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] watchdog: Fix NULL pointer dereference when releasing cdev Message-ID: <20210623113146.GA1316730@roeck-us.net> References: <1624429583-5720-1-git-send-email-curtis.klein@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1624429583-5720-1-git-send-email-curtis.klein@hpe.com> Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On Tue, Jun 22, 2021 at 11:26:23PM -0700, Curtis Klein wrote: > watchdog_hrtimer_pretimeout_stop needs the watchdog device to have a > valid pointer to the watchdog core data to stop the pretimeout hrtimer. > Therefore it needs to be called before the pointers are cleared in > watchdog_cdev_unregister. > > Fixes: 7b7d2fdc8c3e ("watchdog: Add hrtimer-based pretimeout feature") > Reported-by: Colin Ian King > Signed-off-by: Curtis Klein Reviewed-by: Guenter Roeck > --- > drivers/watchdog/watchdog_dev.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c > index 3bab324..ffd8f1a 100644 > --- a/drivers/watchdog/watchdog_dev.c > +++ b/drivers/watchdog/watchdog_dev.c > @@ -1096,6 +1096,8 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd) > watchdog_stop(wdd); > } > > + watchdog_hrtimer_pretimeout_stop(wdd); > + > mutex_lock(&wd_data->lock); > wd_data->wdd = NULL; > wdd->wd_data = NULL; > @@ -1103,7 +1105,6 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd) > > hrtimer_cancel(&wd_data->timer); > kthread_cancel_work_sync(&wd_data->work); > - watchdog_hrtimer_pretimeout_stop(wdd); > > put_device(&wd_data->dev); > } > -- > 2.7.4 >