Re: [PATCH v4] kernel: add kcov code coverage

From: Dmitry Vyukov
Date: Tue Jan 19 2016 - 09:02:49 EST

On Tue, Jan 19, 2016 at 2:05 PM, Kirill A. Shutemov
<kirill@xxxxxxxxxxxxx> wrote:
> On Tue, Jan 19, 2016 at 01:55:43PM +0100, Dmitry Vyukov wrote:
>> >> +static int __init kcov_init(void)
>> >> +{
>> >> + if (!debugfs_create_file("kcov", 0666, NULL, NULL, &kcov_fops)) {
>> >
>> > Why 0666? May be 0600?.
>> The idea is that it can be useful to fuzz-test under a normal user as well.
>> This file is also guarded by debugfs mount permissions. Usually it is mounted
>> as 0700, so normal users can't get access to it.
>> However if one wants to fuzz-test under a normal user, he could mount
>> debugfs as 0777 and get access to this file.
>> I am not very strong about this, though. If you say, I will change it to 0600.
>> I open this file as root at the moment. And we can change it back
>> if/when we better understand a potential use case.
> I think it's safer to make it 0600. It's up to system administrator to
> change permissions, if he wants give this capability to mortals.

Great! I've missed the possibility of chmoding it afterwards. Will
change to 0600 in next version.