linux-kernel - Re: kernel panics with 4.14.X versions

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Message-ID: <20180420102136.a637r6eoghxjqhaf@quack2.suse.cz>
Date:   Fri, 20 Apr 2018 12:21:36 +0200
From:   Jan Kara <jack@...e.cz>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     Jan Kara <jack@...e.cz>,
        Pavlos Parissis <pavlos.parissis@...il.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Robert Kolchmeyer <rkolchmeyer@...gle.com>,
        Guillaume Morin <guillaume@...infr.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "jack@...e.com" <jack@...e.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mszeredi@...hat.com" <mszeredi@...hat.com>
Subject: Re: kernel panics with 4.14.X versions

On Thu 19-04-18 21:37:25, Dexuan Cui wrote:
> > From: Jan Kara
> > Sent: Thursday, April 19, 2018 13:23
> > Good news guys, Robert has just spotted a bug which looks like what I'd
> > expect can cause your lockups / crashes. I've merged his patch to my tree
> > and will push it to Linus for -rc3 so eventually it should land in
> > appropriate stable trees as well. If you are too eager to test it out, it
> > is attached for you to try.
> > 
> > Jan Kara
> 
> The patch's changelog says "... this behavior results in a kernel panic." 
> This sounds like a reference to corrupt memory causes a page fault or
> general protection fault.
> 
> But what I saw is only a lockup rather than a kernel panic:
> watchdog: BUG: soft lockup - CPU#10 stuck for 22s! [java:87260]"
> 
> So I guess what I saw can be a different unresolved issue?

Actually I don't think so. The list iteration simply went through stray
pointer. That can crash but it can also end in an infinite loop, or it can
just randomly corrupt memory. I've seen all these situations with similar
problems. So the fix is definitely worth trying.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR