linux-kernel - Re: [PATCH] clocksource: timer-ti-dm: Fix regression

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Date:   Wed, 8 Jan 2020 03:14:59 +0800
From:   Frank Lee <tiny.windzz@...il.com>
To:     Olof Johansson <olof@...om.net>
Cc:     Tony Lindgren <tony@...mide.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] clocksource: timer-ti-dm: Fix regression

On Tue, Jan 7, 2020 at 5:07 AM Olof Johansson <olof@...om.net> wrote:
>
> On Mon, Jan 6, 2020 at 12:37 PM Tony Lindgren <tony@...mide.com> wrote:
> >
> > Clean-up commit 8c82723414d5 ("clocksource/drivers/timer-ti-dm: Switch to
> > platform_get_irq") caused a regression where we now try to access
> > uninitialized data for timer:
> >
> > drivers/clocksource/timer-ti-dm.c: In function 'omap_dm_timer_probe':
> > drivers/clocksource/timer-ti-dm.c:798:13: warning: 'timer' may be used
> > uninitialized in this function [-Wmaybe-uninitialized]
> >
> > On boot we now get:
> >
> > Unable to handle kernel NULL pointer dereference at virtual address
> > 00000004
> > ...
> > (omap_dm_timer_probe) from [<c061ac7c>] (platform_drv_probe+0x48/0x98)
> > (platform_drv_probe) from [<c0618c04>] (really_probe+0x1dc/0x348)
> > (really_probe) from [<c0618ef4>] (driver_probe_device+0x5c/0x160)
> >
> > Let's fix the issue by moving platform_get_irq to happen after timer has
> > been allocated.
> >
> > Fixes: 8c82723414d5 ("clocksource/drivers/timer-ti-dm: Switch to platform_get_irq")
> > Cc: Yangtao Li <tiny.windzz@...il.com>
> > Signed-off-by: Tony Lindgren <tony@...mide.com>
>
> Acked-by: Olof Johansson <olof@...om.net>

Acked-by: Yangtao Li <tiny.windzz@...il.com>

I am sorry. I will pay attention next time.

>
> > ---
> >
> > I did not notice simlar issue with other patches in the series, but
> > please do double check Yangtao.
>
> Yeah, this even seems to be caught at build (but our builds have been
> so noisy with warnings lately that they're hard to spot):
>
> /build/drivers/clocksource/timer-ti-dm.c: In function 'omap_dm_timer_probe':
> /build/drivers/clocksource/timer-ti-dm.c:798:13: warning: 'timer' may
> be used uninitialized in this function [-Wmaybe-uninitialized]
>   798 |  timer->irq = platform_get_irq(pdev, 0);
>       |  ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> -Olof