linux-kernel - Re: [PATCH] pstore: Convert buf

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Message-ID: <CAKv+Gu8tXHmXrGezZpfkPsVpF09G1XfkpcsxeU2zyP+6OxRLmQ@mail.gmail.com>
Date:   Fri, 21 Dec 2018 16:37:07 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        linux-efi <linux-efi@...r.kernel.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore: Convert buf_lock to semaphore

On Tue, 4 Dec 2018 at 19:06, Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>
> On 2018-12-04 09:23:13 [-0800], Kees Cook wrote:
> > Okay, so, if kmsg_dump() uses rcu_read_lock(), that means efi-pstore
> > can _never_ sleep, and it's nothing to do with pstore internals. :( I
> > guess we just hard-code it, then? And efi-pstore should probably only
> > attach to pstore if it has a nonblock implementation (and warn if one
> > isn't available).
>
> I was about to suggest that. I am not aware if anything else could use
> efi_pstore_write() use that but otherwise you could hardcode it.
>

efivar_entry_set_safe() will only use the default backend if no
non-blocking variant is provided, in which case it assumes that the
default one is non-blocking. Perhaps we should just assign both
function pointers to the same function in this case.