netdev - Re: [PATCH v2 5/8] net: af_can: do not leave a dangling sk pointer in can

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALrw=nG4AmR4M6u1u1a5+cZxM5Vu69PCwbWUoyxaOLhRSypMYg@mail.gmail.com>
Date: Tue, 8 Oct 2024 07:52:58 +0100
From: Ignat Korchagin <ignat@...udflare.com>
To: Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Marcel Holtmann <marcel@...tmann.org>, 
	Johan Hedberg <johan.hedberg@...il.com>, Luiz Augusto von Dentz <luiz.dentz@...il.com>, 
	Oliver Hartkopp <socketcan@...tkopp.net>, Marc Kleine-Budde <mkl@...gutronix.de>, 
	Alexander Aring <alex.aring@...il.com>, Stefan Schmidt <stefan@...enfreihafen.org>, 
	Miquel Raynal <miquel.raynal@...tlin.com>, David Ahern <dsahern@...nel.org>, 
	Willem de Bruijn <willemdebruijn.kernel@...il.com>, linux-bluetooth@...r.kernel.org, 
	linux-can@...r.kernel.org, linux-wpan@...r.kernel.org, 
	kernel-team@...udflare.com, kuniyu@...zon.com, alibuda@...ux.alibaba.com
Subject: Re: [PATCH v2 5/8] net: af_can: do not leave a dangling sk pointer in can_create()

On Tue, Oct 8, 2024 at 3:38 AM Vincent MAILHOL
<mailhol.vincent@...adoo.fr> wrote:
>
> Hi Ignat,
>
> Thanks for the patch.
>
> On Tue. 8 Oct. 2024 at 06:37, Ignat Korchagin <ignat@...udflare.com> wrote:
> > On error can_create() frees the allocated sk object, but sock_init_data()
> > has already attached it to the provided sock object. This will leave a
> > dangling sk pointer in the sock object and may cause use-after-free later.
>
> I was about to suggest that this should be backported to stable, but
> after reading the cover letter, I now understand that this patch is
> more an improvement to avoid false positives on kmemleak & Cie. Maybe
> the description could be a bit more nuanced? After patch 1/8 of this
> series, it seems that the use-after-free is not possible anymore.

If we go with Kuniyuki's suggestion in the cover email to replace the
explicit NULL with DEBUG_NET_WARN_ON_ONCE(sock->sk) in __sock_create()
then use-after-free would be possible again except we will easily
catch it. But I will review the description, when I respin the patches
to net-next as requested by Jakub.

> > Signed-off-by: Ignat Korchagin <ignat@...udflare.com>
>
> See above comment as notwithstanding. This said:
>
> Reviewed-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>

Thank you.

>
> > ---
> >  net/can/af_can.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/net/can/af_can.c b/net/can/af_can.c
> > index 707576eeeb58..01f3fbb3b67d 100644
> > --- a/net/can/af_can.c
> > +++ b/net/can/af_can.c
> > @@ -171,6 +171,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
> >                 /* release sk on errors */
> >                 sock_orphan(sk);
> >                 sock_put(sk);
> > +               sock->sk = NULL;
> >         }
> >
> >   errout:
> > --
> > 2.39.5
> >
> >