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

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Message-Id: <20200106203700.21009-1-tony@atomide.com>
Date:   Mon,  6 Jan 2020 12:37:00 -0800
From:   Tony Lindgren <tony@...mide.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Yangtao Li <tiny.windzz@...il.com>
Subject: [PATCH] clocksource: timer-ti-dm: Fix regression

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>
---

I did not notice simlar issue with other patches in the series, but
please do double check Yangtao.

---
 drivers/clocksource/timer-ti-dm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/timer-ti-dm.c b/drivers/clocksource/timer-ti-dm.c
--- a/drivers/clocksource/timer-ti-dm.c
+++ b/drivers/clocksource/timer-ti-dm.c
@@ -795,14 +795,14 @@ static int omap_dm_timer_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
-	timer->irq = platform_get_irq(pdev, 0);
-	if (timer->irq < 0)
-		return timer->irq;
-
 	timer = devm_kzalloc(dev, sizeof(*timer), GFP_KERNEL);
 	if (!timer)
 		return  -ENOMEM;
 
+	timer->irq = platform_get_irq(pdev, 0);
+	if (timer->irq < 0)
+		return timer->irq;
+
 	timer->fclk = ERR_PTR(-ENODEV);
 	timer->io_base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(timer->io_base))
-- 
2.24.1