From: Dongliang Mu <mudongliangabcd@gmail.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
syzbot+b9cfd1cc5d57ee0a09ab@syzkaller.appspotmail.com,
stable@vger.kernel.org,
"open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] net: xfrm: fix bug in ipcomp_free_scratches
Date: Mon, 16 Aug 2021 19:36:07 +0800 [thread overview]
Message-ID: <CAD-N9QWwmRuPOKZ2BX8ACde4K2GNFUsAWzcciKVG9BwLPcM2-A@mail.gmail.com> (raw)
In-Reply-To: <20210816075346.GA10906@gondor.apana.org.au>
On Mon, Aug 16, 2021 at 3:53 PM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Mon, Aug 16, 2021 at 03:38:29PM +0800, Dongliang Mu wrote:
> >
> > - for_each_possible_cpu(i)
> > - vfree(*per_cpu_ptr(scratches, i));
> > + for_each_possible_cpu(i) {
> > + void *scratch = *per_cpu_ptr(scratches, i);
> > + if (!scratch)
> > + vfree(scratch);
> > + }
>
> This patch is unnecessary. Please check the implementation of
> vfree, it already checks for NULL pointers just like most of our
> free primitives.
Hi Herbert,
since there is no reproducer in the syzbot, I guess the problem might be:
if vmalloc_node in the ipcomp_alloc_scratches returns a NULL pointer,
it directly returns NULL without updating the per_cpu_ptr(scratches,
i).
Therefore, in the ipcomp_free_scratches, vfree will take an invalid
and outdated per_cpu_ptr as its argument, leading to the bug - BUG:
unable to handle kernel paging request in ipcomp_free_scratches.
Any idea?
>
> Cheers,
> --
> Email: Herbert Xu <herbert@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
prev parent reply other threads:[~2021-08-16 11:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 7:38 [PATCH] net: xfrm: fix bug in ipcomp_free_scratches Dongliang Mu
2021-08-16 7:53 ` Herbert Xu
2021-08-16 9:35 ` Dongliang Mu
2021-08-16 11:36 ` Dongliang Mu [this message]
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