On Sun, Aug 15, 2021 at 04:13:45AM +0900, Stanislav German-Evtushenko wrote: > If userspace opens the watchdog device self-feeding stops. Sometimes > opening the device happens by accident, e.g. by mistakenly running grep > recursively in a wrong directory which leads to the server being reset. > > Watchdog device does not handle read operation therefore the issue can be > prevented by requiring the device to be opened for writing: > > - Prevent opening the device without FMODE_WRITE > > Signed-off-by: Stanislav German-Evtushenko <ginermail@xxxxxxxxx> NACK. That would be a major undocumented ABI change. Opening /dev/watchdog for reading can be and is used today to test a watchdog. Guenter > --- > drivers/watchdog/watchdog_dev.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c > index 3bab32485273..28b88542a4d0 100644 > --- a/drivers/watchdog/watchdog_dev.c > +++ b/drivers/watchdog/watchdog_dev.c > @@ -835,6 +835,10 @@ static int watchdog_open(struct inode *inode, struct file *file) > bool hw_running; > int err; > > + /* Must be open for writing */ > + if (!(file->f_mode & FMODE_WRITE)) > + return -EINVAL; > + > /* Get the corresponding watchdog device */ > if (imajor(inode) == MISC_MAJOR) > wd_data = old_wd_data; > > base-commit: cf813c67d9619fd474c785698cbed543b94209dd > -- > 2.25.1 >
