potential null dereference in sysfs_override_clocksource()

[Posted July 21, 2009 by corbet]

From:		Dan Carpenter <error27-AT-gmail.com>
To:		linux-kernel-AT-vger.kernel.org
Subject:		potential null dereference in sysfs_override_clocksource()
Date:		Sun, 19 Jul 2009 16:04:48 +0300 (EAT)
Message-ID:		<alpine.DEB.2.00.0907191545580.12306@bicker>
Archive‑link:		Article

Hello,

I am testing a source checker (http://repo.or.cz/w/smatch.git).

It found an issue in sysfs_override_clocksource() from 
kernel/time/clocksource.c.  If "len" is zero then "ovr" is null and 
checking ovr->flags will oops on line 517.

kernel/time/clocksource.c
   516          if (tick_oneshot_mode_active() &&
   517              !(ovr->flags & CLOCK_SOURCE_VALID_FOR_HRES)) {
   518                  printk(KERN_WARNING "%s clocksource is not HRT compatible. "

regards,
dan carpenter