linux-kernel - Re: [PATCH v2] firmware: fix sending -ERESTARTSYS due to signal on fallback

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Date:   Wed, 24 May 2017 15:00:18 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Daniel Wagner <wagi@...om.org>,
        David Woodhouse <dwmw2@...radead.org>,
        jewalt@...innovations.com, rafal@...ecki.pl,
        arend.vanspriel@...adcom.com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, yi1.li@...ux.intel.com,
        atull@...nsource.altera.com, moritz.fischer@...us.com,
        Petr Mladek <pmladek@...e.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        David Howells <dhowells@...hat.com>,
        Peter Jones <pjones@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Alan Cox <alan@...ux.intel.com>, "Ted Ts'o" <tytso@....edu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Martin Fuzzey <mfuzzey@...keon.com>,
        "stable # 4 . 0" <stable@...r.kernel.org>
Subject: Re: [PATCH v2] firmware: fix sending -ERESTARTSYS due to signal on fallback

On Wed, May 24, 2017 at 2:40 PM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
> From: Martin Fuzzey <mfuzzey@...keon.com>
>
> Commit 0cb64249ca500 ("firmware_loader: abort request if wait_for_completion
> is interrupted") added via 4.0 added support to abort the fallback mechanism
> when a signal was detected and wait_for_completion_interruptible() returned
> -ERESTARTSYS. Although the abort was effective we were unfortunately never
> really propagating this error though and as such userspace could not know
> why the abort happened.

Can you give a simple example of what's going on and why it matters?

ERESTARTSYS and friends are highly magical, and I'm not convinced that
allowing _request_firmware_load to return -ERESTARTSYS is actually a
good idea.  What if there are system calls that can't handle this
style of restart that start being restarted as a result?