linux-kernel - Re: [PATCH v8 1/4] Landlock: Add abstract unix socket connect restriction

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Message-ID: <CAG48ez39+ts9pNVvAxXcbk6X5_+s_yBXPUW-ZUNRxQq3aJAyrQ@mail.gmail.com>
Date: Tue, 6 Aug 2024 21:36:52 +0200
From: Jann Horn <jannh@...gle.com>
To: Tahera Fahimi <fahimitahera@...il.com>
Cc: outreachy@...ts.linux.dev, mic@...ikod.net, gnoack@...gle.com, 
	paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com, 
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bjorn3_gh@...tonmail.com, netdev@...r.kernel.org
Subject: Re: [PATCH v8 1/4] Landlock: Add abstract unix socket connect restriction

On Fri, Aug 2, 2024 at 6:03 AM Tahera Fahimi <fahimitahera@...il.com> wrote:
> This patch introduces a new "scoped" attribute to the landlock_ruleset_attr
> that can specify "LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET" to scope
> abstract Unix sockets from connecting to a process outside of
> the same landlock domain. It implements two hooks, unix_stream_connect
> and unix_may_send to enforce this restriction.
[...]
> +static bool check_unix_address_format(struct sock *const sock)
> +{
> +       struct unix_address *addr = unix_sk(sock)->addr;
> +
> +       if (!addr)
> +               return true;
> +
> +       if (addr->len > sizeof(AF_UNIX)) {
> +               /* handling unspec sockets */
> +               if (!addr->name[0].sun_path)
> +                       return true;

addr->name[0] is a "struct sockaddr_un", whose member "sun_path" is an
array member, not a pointer. If "addr" is a valid pointer,
"addr->name[0].sun_path" can't be NULL.


> +               if (addr->name[0].sun_path[0] == '\0')
> +                       if (!sock_is_scoped(sock))
> +                               return false;
> +       }
> +
> +       return true;
> +}