linux-kernel - Re: [PATCH] net: xfrm: assign the per_cpu

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Message-ID: <CAD-N9QVRuBAER0o1H6eTre_YOU+4mbHuj3homHno0UHiJrXuUg@mail.gmail.com>
Date:   Wed, 18 Aug 2021 18:39:25 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        syzbot+b9cfd1cc5d57ee0a09ab@...kaller.appspotmail.com,
        stable@...r.kernel.org,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: xfrm: assign the per_cpu_ptr pointer before return

On Wed, Aug 18, 2021 at 11:32 AM Herbert Xu <herbert@...dor.apana.org.au> wrote:
>
> On Wed, Aug 18, 2021 at 11:25:53AM +0800, Dongliang Mu wrote:
> >
> > diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c
> > index cb40ff0ff28d..01dbec70dfba 100644
> > --- a/net/xfrm/xfrm_ipcomp.c
> > +++ b/net/xfrm/xfrm_ipcomp.c
> > @@ -223,9 +223,9 @@ static void * __percpu *ipcomp_alloc_scratches(void)
> >               void *scratch;
> >
> >               scratch = vmalloc_node(IPCOMP_SCRATCH_SIZE, cpu_to_node(i));
> > +             *per_cpu_ptr(scratches, i) = scratch;
> >               if (!scratch)
> >                       return NULL;
> > -             *per_cpu_ptr(scratches, i) = scratch;
>
> scratches comes from alloc_percpu so it should already be zeroed.

Correct.

:\ Then I have no idea how this crash occurs. This crash report does
not have any reproducer. It seems like a random crash, but I am not
sure.

If you have any patch for this crash, please let me know.

>
> Cheers,
> --
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt