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Subject: Re: "rfkill: add a reason to the HW rfkill state" breaks userspace
To:     Benjamin Berg <bberg@redhat.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        "Grumbach, Emmanuel" <emmanuel.grumbach@intel.com>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>
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From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <5064e714-1e1e-237a-b2e4-00123f95e8bf@redhat.com>
Date:   Wed, 14 Apr 2021 13:17:34 +0200
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Hi,

On 4/14/21 12:46 PM, Benjamin Berg wrote:
> Hi,
> 
> On Wed, 2021-04-14 at 12:29 +0200, Hans de Goede wrote:
>> On 4/14/21 11:52 AM, Benjamin Berg wrote:
>>> [SNIP]
>>>
>>> That said, the g-s-d event handler is checking the size of the read
>>> against the struct size. This is obviously wrong, it should only
>>> check
>>> that the read was successful (or check for >= V1 size).
>>
>> Right this is what I was referring to a g-s-d compiled against the
>> new headers with a struct size of 9 will read 8 bytes on an old
>> kernel
>> and that will fail the len check, so it won't work.
>>
>> But this will actually never happen as I just noticed that g-s-d
>> uses a private rfkill.h copy with the old 8 bytes struct definition.
>>
>> So with the buffered-io disabled everything should work fine,
>> see my other email in this thread.
> 
> OK, so at least that part of the fix should be backported to older
> release branches.

Ack, that fix should be backported to fix issues with newer
kernels and then everything should work fine.

Regards,

Hans