Re: [PATCH] PCI: prevent out of bounds access in numa_node override

[Prarit Bhargava <prarit@redhat.com>]

On 10/06/2015 03:36 PM, Bjorn Helgaas wrote:
> Hi Sasha,
> 
> On Sun, Oct 04, 2015 at 05:49:29PM -0400, Sasha Levin wrote:
>> Commit 63692df1 ("PCI: Allow numa_node override via sysfs") didn't check that
>> the numa node provided by userspace is valid. Passing a node number too high
>> would attempt to access invalid memory and trigger a kernel panic.
>>
>> Fixes: 63692df1 ("PCI: Allow numa_node override via sysfs")
>> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
>> ---
>>  drivers/pci/pci-sysfs.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
>> index 312f23a..e9abca8 100644
>> --- a/drivers/pci/pci-sysfs.c
>> +++ b/drivers/pci/pci-sysfs.c
>> @@ -216,7 +216,7 @@ static ssize_t numa_node_store(struct device *dev,
>>  	if (ret)
>>  		return ret;
>>  
>> -	if (!node_online(node))
>> +	if (node > MAX_NUMNODES || !node_online(node))
> 
> This needs to be "node >= MAX_NUMNODES", doesn't it?  I'll fix it up if
> you agree.

Not a strenuous objection, but I don't see much bound checking using
MAX_NUMNODES in the kernel outside of the core numa area.  Is fixing
node_online() with bounds checking a better option here so that other callers
get the fix?  I would have thought that calling node_online() with node >
MAX_NUMNODES should be safe to call.

P.

> 
> Looks like a candidate for stable.
> 
>>  		return -EINVAL;
>>  
>>  	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
>> -- 
>> 1.7.10.4
>>
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