Messages in this thread | | | Date | Tue, 03 Apr 2012 17:21:11 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: [PATCH] cpuidle: Avoid possible NULL pointer dereference in __cpuidle_register_device() |
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On 04/03/2012 01:01 AM, Daniel Lezcano wrote:
> On 04/02/2012 04:44 PM, Srivatsa S. Bhat wrote: >> In __cpuidle_register_device(), "dev->cpu" is used before checking if >> dev is >> non-NULL. Fix it. >> >> Signed-off-by: Srivatsa S. Bhat<srivatsa.bhat@linux.vnet.ibm.com> >> --- > > That should be fixed at the caller level. Usually, static function does > not check the function parameters, it is up to the exported function to > do that. It is supposed the static functions are called with valid > parameters. >
Ok, good point! I hadn't thought about that.. I just happened to notice that in __cpuidle_register_device(), the dev == NULL check is performed _after_ dereferencing it, which made the check useless. So I tried to fix that within that function. But thanks for pointing out the semantics..
> There are two callers for __cpuidle_register_device: > * cpuidle_register_device > * cpuidle_enable_device > > Both of them do not check 'dev' is a valid parameter. They should as > they are exported and could be used by an external module. IMHO, BUG_ON > could be used here if dev == NULL. >
BUG_ON? That would crash the system.. which might be unnecessary..
How about checking if dev == NULL in the 2 callers like you suggested and returning -EINVAL if dev is indeed NULL?
(And of course no checks for dev == NULL in __cpuidle_register_device).
> >> drivers/cpuidle/cpuidle.c | 3 ++- >> 1 files changed, 2 insertions(+), 1 deletions(-) >> >> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c >> index 87411ce..75b381e 100644 >> --- a/drivers/cpuidle/cpuidle.c >> +++ b/drivers/cpuidle/cpuidle.c >> @@ -372,7 +372,7 @@ EXPORT_SYMBOL_GPL(cpuidle_disable_device); >> static int __cpuidle_register_device(struct cpuidle_device *dev) >> { >> int ret; >> - struct device *cpu_dev = get_cpu_device((unsigned long)dev->cpu); >> + struct device *cpu_dev; >> struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver(); >> >> if (!dev) >> @@ -380,6 +380,7 @@ static int __cpuidle_register_device(struct >> cpuidle_device *dev) >> if (!try_module_get(cpuidle_driver->owner)) >> return -EINVAL; >> >> + cpu_dev = get_cpu_device((unsigned long)dev->cpu); >> init_completion(&dev->kobj_unregister); >> >> per_cpu(cpuidle_devices, dev->cpu) = dev; >> > >
Thank you for the review!
Regards, Srivatsa S. Bhat
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