linux-kernel - Re: [PATCH v3] firmware_loader: fix use-after-free in firmware_fallback

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Date:   Fri, 23 Apr 2021 12:44:21 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Anirudh Rayabharam <mail@...rudhrb.com>,
        Shuah Khan <shuah@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Junyong Sun <sunjy516@...il.com>,
        syzbot+de271708674e2093097b@...kaller.appspotmail.com,
        linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v3] firmware_loader: fix use-after-free in
 firmware_fallback_sysfs

On 4/23/21 12:40 PM, Luis Chamberlain wrote:
> On Wed, Apr 14, 2021 at 09:26:55AM -0600, Shuah Khan wrote:
>> On 4/14/21 6:55 AM, Luis Chamberlain wrote:
>>> In either case I documented well *why* we do these error checks
>>> before sending a code to userspace on fw_sysfs_wait_timeout() since
>>> otherwise it would be easy to regress that code, so please also
>>> document that as I did.
>>>
>>> I'll re-iterate again also:
>>>
>>> 	Shuah's commit 0542ad88fbdd81bb ("firmware loader: Fix
>>> 	_request_firmware_load() return val for fw load abort") also wanted to
>>> 	distinguish the timeout vs -ENOMEM, but for some reason in the timeout
>>> 	case -EAGAIN was being sent back to userspace. I am no longer sure if
>>> 	that is a good idea, but since we started doing that at some point I
>>> 	guess we want to keep that behaviour.
>>>
>>> Shuah, can you think of any reason to retain -EAGAIN other than you
>>> introduced it here? If there's no real good reason I think it can
>>> simplify the error handling here. But, we *would* change what we do
>>> to userspace... and for that reason we may have to live with it.
>>>
>>
>> As I recall the reason for this patch was to be able to differentiate
>> between timing out vs no memory case when driver was attempting to
>> load firmware. I wish I added why to the change log.
>>
>> The code seems to have changed a lot since my commit. I will take a look
>> at the closely and let you know if this is still necessary late on
>> today.
> 
> Shuah, *poke*
> 
Luis,

I responded to you a week ago. Let me resend the message.

thanks,
-- Shuah