linux-kernel - Re: [PATCH 4/8] pstore: Alert on backend write error

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Message-ID: <202210061644.6FB59099@keescook>
Date:   Thu, 6 Oct 2022 16:44:38 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        kernel-dev@...lia.com, kernel@...ccoli.net, anton@...msg.org,
        ccross@...roid.com, tony.luck@...el.com
Subject: Re: [PATCH 4/8] pstore: Alert on backend write error

On Thu, Oct 06, 2022 at 08:34:44PM -0300, Guilherme G. Piccoli wrote:
> On 06/10/2022 20:27, Kees Cook wrote:
> > [...]
> >> --- a/fs/pstore/platform.c
> >> +++ b/fs/pstore/platform.c
> >> @@ -463,6 +463,9 @@ static void pstore_dump(struct kmsg_dumper *dumper,
> >>  		if (ret == 0 && reason == KMSG_DUMP_OOPS) {
> >>  			pstore_new_entry = 1;
> >>  			pstore_timer_kick();
> >> +		} else {
> >> +			pr_err_once("backend (%s) writing error (%d)\n",
> >> +				    psinfo->name, ret);
> > 
> > We're holding a spinlock here, so doing a pr_*() call isn't a great
> > idea. It's kind of not a great idea to try to write to the log in the
> > middle of a dump either, but we do attempt it at the start.
> > 
> > Perhaps keep a saved_ret or something and send it after the spin lock is
> > released?
> > 
> 
> Hi Kees, thanks a lot for the very quick review!!
> 
> Agree with you, I'll rework this one.
> Do you agree with showing only a single error? For me makes sense since
> we just wanna hint advanced users (+ people-debugging-pstore heh) that
> something went wrong.

Yeah, I agree -- it's going to be for folks working on pstore code. :)

-- 
Kees Cook