On Thu, Apr 15, 2021 at 05:50:32PM -0700, Guenter Roeck wrote:
> On 4/15/21 5:12 PM, rentao.bupt@xxxxxxxxx wrote:
> > From: Tao Ren <rentao.bupt@xxxxxxxxx>
> >
> > Fix the time comparison (timeout vs. max_hw_heartbeat_ms) in set_timeout
> > handler to avoid potential integer overflow when the supplied timeout is
> > greater than aspeed's maximum allowed timeout (4294 seconds).
> >
> > Fixes: efa859f7d786 ("watchdog: Add Aspeed watchdog driver")
> > Reported-by: Amithash Prasad <amithash@xxxxxx>
> > Signed-off-by: Tao Ren <rentao.bupt@xxxxxxxxx>
> > ---
> > drivers/watchdog/aspeed_wdt.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
> > index 7e00960651fa..9f77272dc906 100644
> > --- a/drivers/watchdog/aspeed_wdt.c
> > +++ b/drivers/watchdog/aspeed_wdt.c
> > @@ -145,9 +145,8 @@ static int aspeed_wdt_set_timeout(struct watchdog_device *wdd,
> > struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);
> > u32 actual;
> >
> > - wdd->timeout = timeout;
> > -
> > - actual = min(timeout, wdd->max_hw_heartbeat_ms * 1000);
> > + actual = min(timeout, wdd->max_hw_heartbeat_ms / 1000);
> > + wdd->timeout = actual;
> >
> > writel(actual * WDT_RATE_1MHZ, wdt->base + WDT_RELOAD_VALUE);
> > writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);
> >
>
> If the provided timeout is larger than the supported hardware timeout,
> the watchdog core will ping the hardware on behalf of userspace.
> The above code would defeat that mechanism for no good reason.
>
> NACK.
>
> Guenter
Thanks Guenter for Joel for the quick review!
The integer overflow happens at (actual * WDT_RATE_1MHZ). For example,
if a user tries to set timeout to 4295 seconds, then the hardware would
be programmed to timeout after about 32 milliseconds. I would say this
behavior is not expected?
Cheers,
Tao
