linux-kernel - Re: [EXT] [PATCH] net: atlantic: always deep reset on pm op, fixing null deref regression

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Date:   Thu, 5 May 2022 09:04:48 +0200
From:   Igor Russkikh <irusskikh@...vell.com>
To:     Manuel Ullmann <labre@...teo.de>
CC:     <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <regressions@...ts.linux.dev>, <davem@...emloft.net>,
        <kuba@...nel.org>, <pabeni@...hat.com>,
        Jordan Leppert <jordanleppert@...tonmail.com>,
        Holger Hoffstätte <holger@...lied-asynchrony.com>,
        koo5 <kolman.jindrich@...il.com>,
        Dmitry Bezrukov <dbezrukov@...vell.com>
Subject: Re: [EXT] [PATCH] net: atlantic: always deep reset on pm op, fixing
 null deref regression


> The impact of this regression is the same for resume that I saw on
> thaw: the kernel hangs and nothing except SysRq rebooting can be done.
> 
> The null deref occurs at the same position as on thaw.
> BUG: kernel NULL pointer dereference
> RIP: aq_ring_rx_fill+0xcf/0x210 [atlantic]
> 
> Fixes regression in cbe6c3a8f8f4 ("net: atlantic: invert deep par in
> pm functions, preventing null derefs"), where I disabled deep pm
> resets in suspend and resume, trying to make sense of the
> atl_resume_common deep parameter in the first place.
> 
> It turns out, that atlantic always has to deep reset on pm operations
> and the parameter is useless. Even though I expected that and tested
> resume, I screwed up by kexec-rebooting into an unpatched kernel, thus
> missing the breakage.
> 
> This fixup obsoletes the deep parameter of atl_resume_common, but I
> leave the cleanup for the maintainers to post to mainline.
> 
> PS: I'm very sorry for this regression.

Hi Manuel,

Unfortunately I've missed to review and comment on previous patch - it was too quickly accepted.

I'm still in doubt on your fixes, even after rereading the original problem.
Is it possible for you to test this with all the possible combinations?
suspend/resume with device up/down,
hibernate/restore with device up/down?

I'll try to do the same on our side, but we don't have much resources for that now unfortunately..


> Fixes: cbe6c3a8f8f4315b96e46e1a1c70393c06d95a4c

That tag format is incorrect I think..

Igor