From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-bc0f.mail.infomaniak.ch (smtp-bc0f.mail.infomaniak.ch [45.157.188.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 744C437BE8B for ; Mon, 9 Feb 2026 18:02:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.157.188.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770660121; cv=none; b=k9AG2hYxSWmc4VsEs3AIc6+wSwSTVlCoObz85Go4Ms+Yswx9d/MPR7F6x4W6B/mvOeRsfaRQyBd9QDJ5+kTwpK/VRm91+saoutUVs+ouIt5XX/uRNoOqQ36rqHBq1QpC/tRCjDRmohb9Rr2MPeD7J4ExBSsKi64bxomqGm7EQyc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770660121; c=relaxed/simple; bh=JYzv9E94IkXmjniou/e10LbOmoZj80DqckJ2LgzhWNE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=p2FxJgx1JZCDtUdYtp0IawY7GQxIlwujm1MeBYMDouIl3AIGo3zrvw30zBtbsqPvNidUxepw/ZvCw+h+YkB9vzD/dRTZK3kM2KEutveTYu+O+OpPBkCrjTLzqk88TJKY1juqPphs1kIm9ubwuOXW63yiUAoHx3UYMKgIFHj3F5k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net; spf=pass smtp.mailfrom=digikod.net; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b=HCCOQ+uF; arc=none smtp.client-ip=45.157.188.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=digikod.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b="HCCOQ+uF" Received: from smtp-4-0001.mail.infomaniak.ch (smtp-4-0001.mail.infomaniak.ch [10.7.10.108]) by smtp-4-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4f8sgy3Wnkz49P; Mon, 9 Feb 2026 18:51:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digikod.net; s=20191114; t=1770659486; bh=BBYhcLwsTs9OhGHaQVQ/SWzdyTzVaDUYDHQ0lCXjoYc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HCCOQ+uFlE3610zU1m1PJMXUXdw16rzusoKTVwbWiqvGpNwmdJPCaEh1V2AUWg4le WdKt8jIhcysSwSB4DxGbgIL3+yY8rIj4ilqL0/XC2n+bwqiz8unJdQCUZ8f6zNGzR+ qr4qzVEKkVTlMSCBL0FFI+0YodrWTM9+Xdz3w9Pg= Received: from unknown by smtp-4-0001.mail.infomaniak.ch (Postfix) with ESMTPA id 4f8sgx2DlHzZl4; Mon, 9 Feb 2026 18:51:25 +0100 (CET) Date: Mon, 9 Feb 2026 18:51:21 +0100 From: =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= To: =?utf-8?Q?G=C3=BCnther?= Noack Cc: John Johansen , Paul Moore , James Morris , "Serge E . Hallyn" , Tingmao Wang , Justin Suess , linux-security-module@vger.kernel.org, Samasth Norway Ananda , Matthieu Buffet , Mikhail Ivanov , konstantin.meskhidze@huawei.com, Demi Marie Obenour , Alyssa Ross , Jann Horn , Tahera Fahimi , Simon Horman , netdev@vger.kernel.org, Alexander Viro , Christian Brauner Subject: Re: [PATCH v4 1/6] lsm: Add LSM hook security_unix_find Message-ID: <20260209.yeeh3ieDuz9u@digikod.net> References: <20260208231017.114343-1-gnoack3000@gmail.com> <20260208231017.114343-2-gnoack3000@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260208231017.114343-2-gnoack3000@gmail.com> X-Infomaniak-Routing: alpha On Mon, Feb 09, 2026 at 12:10:11AM +0100, Günther Noack wrote: > From: Justin Suess > > Add a LSM hook security_unix_find. > > This hook is called to check the path of a named unix socket before a > connection is initiated. The peer socket may be inspected as well. > > Why existing hooks are unsuitable: > > Existing socket hooks, security_unix_stream_connect(), > security_unix_may_send(), and security_socket_connect() don't provide > TOCTOU-free / namespace independent access to the paths of sockets. > > (1) We cannot resolve the path from the struct sockaddr in existing hooks. > This requires another path lookup. A change in the path between the > two lookups will cause a TOCTOU bug. > > (2) We cannot use the struct path from the listening socket, because it > may be bound to a path in a different namespace than the caller, > resulting in a path that cannot be referenced at policy creation time. > > Cc: Günther Noack > Cc: Tingmao Wang > Signed-off-by: Justin Suess > --- > include/linux/lsm_hook_defs.h | 5 +++++ > include/linux/security.h | 11 +++++++++++ > net/unix/af_unix.c | 9 +++++++++ > security/security.c | 20 ++++++++++++++++++++ > 4 files changed, 45 insertions(+) > > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > index 8c42b4bde09c..7a0fd3dbfa29 100644 > --- a/include/linux/lsm_hook_defs.h > +++ b/include/linux/lsm_hook_defs.h > @@ -317,6 +317,11 @@ LSM_HOOK(int, 0, post_notification, const struct cred *w_cred, > LSM_HOOK(int, 0, watch_key, struct key *key) > #endif /* CONFIG_SECURITY && CONFIG_KEY_NOTIFICATIONS */ > > +#if defined(CONFIG_SECURITY_NETWORK) && defined(CONFIG_SECURITY_PATH) > +LSM_HOOK(int, 0, unix_find, const struct path *path, struct sock *other, > + int flags) > +#endif /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ > + > #ifdef CONFIG_SECURITY_NETWORK > LSM_HOOK(int, 0, unix_stream_connect, struct sock *sock, struct sock *other, > struct sock *newsk) > diff --git a/include/linux/security.h b/include/linux/security.h > index 83a646d72f6f..99a33d8eb28d 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -1931,6 +1931,17 @@ static inline int security_mptcp_add_subflow(struct sock *sk, struct sock *ssk) > } > #endif /* CONFIG_SECURITY_NETWORK */ > > +#if defined(CONFIG_SECURITY_NETWORK) && defined(CONFIG_SECURITY_PATH) > + > +int security_unix_find(const struct path *path, struct sock *other, int flags); > + > +#else /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ > +static inline int security_unix_find(const struct path *path, struct sock *other, int flags) > +{ > + return 0; > +} > +#endif /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ > + > #ifdef CONFIG_SECURITY_INFINIBAND > int security_ib_pkey_access(void *sec, u64 subnet_prefix, u16 pkey); > int security_ib_endport_manage_subnet(void *sec, const char *name, u8 port_num); > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c > index d0511225799b..db9d279b3883 100644 > --- a/net/unix/af_unix.c > +++ b/net/unix/af_unix.c > @@ -1226,10 +1226,19 @@ static struct sock *unix_find_bsd(struct sockaddr_un *sunaddr, int addr_len, > if (!S_ISSOCK(inode->i_mode)) > goto path_put; > > + err = -ECONNREFUSED; We don't see it in this patch but err is already set to -ECONNREFUSED. This line might be confusing, and unrelated to the goal of this patch, so we should remove it. > sk = unix_find_socket_byinode(inode); > if (!sk) > goto path_put; > > + /* > + * We call the hook because we know that the inode is a socket > + * and we hold a valid reference to it via the path. This comment can be alligned with 80 columns. > + */ > + err = security_unix_find(&path, sk, flags); This hook makes sense and is quite generic. > + if (err) > + goto sock_put; > + > err = -EPROTOTYPE; > if (sk->sk_type == type) > touch_atime(&path); > diff --git a/security/security.c b/security/security.c > index 31a688650601..9e9515955098 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -4731,6 +4731,26 @@ int security_mptcp_add_subflow(struct sock *sk, struct sock *ssk) > > #endif /* CONFIG_SECURITY_NETWORK */ > > +#if defined(CONFIG_SECURITY_NETWORK) && defined(CONFIG_SECURITY_PATH) > +/* This should be a docstring like other hooks: /** > + * security_unix_find() - Check if a named AF_UNIX socket can connect > + * @path: path of the socket being connected to > + * @other: peer sock > + * @flags: flags associated with the socket > + * > + * This hook is called to check permissions before connecting to a named > + * AF_UNIX socket. > + * > + * Return: Returns 0 if permission is granted. > + */ > +int security_unix_find(const struct path *path, struct sock *other, int flags) > +{ > + return call_int_hook(unix_find, path, other, flags); > +} > +EXPORT_SYMBOL(security_unix_find); > + > +#endif /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ > + > #ifdef CONFIG_SECURITY_INFINIBAND > /** > * security_ib_pkey_access() - Check if access to an IB pkey is allowed > -- > 2.52.0 > >