linux-kernel - Re: [PATCH] selinux: read and write sid under lock

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Message-ID: <CAHC9VhT-VA74h90ScjwO11g7b0pmCjzhVYWKHmkKqD2LLio98g@mail.gmail.com>
Date: Mon, 10 Mar 2025 16:18:31 -0400
From: Paul Moore <paul@...l-moore.com>
To: Edward Adam Davis <eadavis@...com>, Stephen Smalley <stephen.smalley.work@...il.com>
Cc: syzbot+00c633585760c05507c3@...kaller.appspotmail.com, 
	linux-kernel@...r.kernel.org, omosnace@...hat.com, selinux@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] selinux: read and write sid under lock

On Mon, Mar 10, 2025 at 3:53 PM Stephen Smalley
<stephen.smalley.work@...il.com> wrote:
> On Sat, Mar 8, 2025 at 11:55 PM Edward Adam Davis <eadavis@...com> wrote:
> >
> > syzbot reported a data-race in selinux_socket_post_create /
> > selinux_socket_sock_rcv_skb. [1]
> >
> > When creating the socket path and receiving the network data packet path,
> > effective data access protection is not performed when reading and writing
> > the sid, resulting in a race condition.
> >
> > Add a lock to synchronize the two.

...

> > Reported-by: syzbot+00c633585760c05507c3@...kaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=00c633585760c05507c3
> > Signed-off-by: Edward Adam Davis <eadavis@...com>
> > ---
> >  security/selinux/hooks.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > index 7b867dfec88b..ea5d0273f9d5 100644
> > --- a/security/selinux/hooks.c
> > +++ b/security/selinux/hooks.c
> > @@ -4677,8 +4677,10 @@ static int selinux_socket_post_create(struct socket *sock, int family,
> >
> >         if (sock->sk) {
> >                 sksec = selinux_sock(sock->sk);
> > +               spin_lock(&sksec->lock);
>
> You didn't include the diff that adds this lock field to
> sk_security_struct, but aside from that, I would suggest something
> lighter-weight like READ_ONCE/WRITE_ONCE if possible.

Yes, please don't add a spinlock to something that is potentially
going to be hit on every packet entering the system.

-- 
paul-moore.com