Merge: landlock: update landlock-lsm headers for api v5 and v6 in RHEL-9

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/7037

JIRA: https://issues.redhat.com/browse/RHEL-94688

Customer request to update landlock-lsm headers to better match RHEL-10

Omitted-fix: 8d66506 ("bpf: syzkaller found null ptr deref in unix_bpf proto add")
Omitted-fix: 16b2f26 ("bpf: sockmap, fix proto update hook to avoid dup calls")

Signed-off-by: Ryan Sullivan <rysulliv@redhat.com>

Approved-by: Felix Maurer <fmaurer@redhat.com>
Approved-by: Jay Shin <jaeshin@redhat.com>
Approved-by: Ondrej Mosnáček <omosnacek@gmail.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Augusto Caringi <acaringi@redhat.com>

Author: caringi

Documentation/userspace-api/landlock.rst

@@ -8,7 +8,7 @@ Landlock: unprivileged access control
 =====================================
 
 :Author: Mickaël Salaün
-:Date: April 2024
+:Date: September 2024
 
 The goal of Landlock is to enable to restrict ambient rights (e.g. global
 filesystem or network access) for a set of processes.  Because Landlock
@@ -81,6 +81,8 @@ to be explicit about the denied-by-default access rights.
         .handled_access_net =
             LANDLOCK_ACCESS_NET_BIND_TCP |
             LANDLOCK_ACCESS_NET_CONNECT_TCP,
+        .scoped =
+            LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET,
     };
 
 Because we may not know on which kernel version an application will be
@@ -119,6 +121,10 @@ version, and only use the available subset of access rights:
     case 4:
         /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */
         ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
+        __attribute__((fallthrough));
+    case 5:
+        /* Removes LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET for ABI < 6 */
+        ruleset_attr.scoped &= ~LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET;
     }
 
 This enables to create an inclusive ruleset that will contain our rules.
@@ -306,6 +312,33 @@ To be allowed to use :manpage:`ptrace(2)` and related syscalls on a target
 process, a sandboxed process should have a subset of the target process rules,
 which means the tracee must be in a sub-domain of the tracer.
 
+IPC scoping
+-----------
+
+Similar to the implicit `Ptrace restrictions`_, we may want to further restrict
+interactions between sandboxes. Each Landlock domain can be explicitly scoped
+for a set of actions by specifying it on a ruleset.  For example, if a
+sandboxed process should not be able to :manpage:`connect(2)` to a
+non-sandboxed process through abstract :manpage:`unix(7)` sockets, we can
+specify such restriction with ``LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET``.
+
+A sandboxed process can connect to a non-sandboxed process when its domain is
+not scoped. If a process's domain is scoped, it can only connect to sockets
+created by processes in the same scope.
+
+A connected datagram socket behaves like a stream socket when its domain is
+scoped, meaning if the domain is scoped after the socket is connected , it can
+still :manpage:`send(2)` data just like a stream socket.  However, in the same
+scenario, a non-connected datagram socket cannot send data (with
+:manpage:`sendto(2)`) outside its scope.
+
+A process with a scoped domain can inherit a socket created by a non-scoped
+process. The process cannot connect to this socket since it has a scoped
+domain.
+
+IPC scoping does not support exceptions, so if a domain is scoped, no rules can
+be added to allow access to resources or processes outside of the scope.
+
 Truncating files
 ----------------
 
@@ -404,7 +437,7 @@ Access rights
 -------------
 
 .. kernel-doc:: include/uapi/linux/landlock.h
-    :identifiers: fs_access net_access
+    :identifiers: fs_access net_access scope
 
 Creating a new ruleset
 ----------------------
@@ -541,6 +574,13 @@ earlier ABI.
 Starting with the Landlock ABI version 5, it is possible to restrict the use of
 :manpage:`ioctl(2)` using the new ``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right.
 
+Abstract UNIX socket scoping (ABI < 6)
+--------------------------------------
+
+Starting with the Landlock ABI version 6, it is possible to restrict
+connections to an abstract :manpage:`unix(7)` socket by setting
+``LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET`` to the ``scoped`` ruleset attribute.
+
 .. _kernel_support:
 
 Kernel support

include/linux/skmsg.h

@@ -106,6 +106,7 @@ struct sk_psock {
 	struct mutex			work_mutex;
 	struct sk_psock_work_state	work_state;
 	struct work_struct		work;
+	struct sock			*sk_pair;
 	struct rcu_work			rwork;
 };
 

include/net/af_unix.h

@@ -88,6 +88,7 @@ static inline void unix_state_lock_nested(struct sock *sk,
 	spin_lock_nested(&unix_sk(sk)->lock, subclass);
 }
 
+#define unix_peer(sk) (unix_sk(sk)->peer)
 #define peer_wait peer_wq.wait
 
 long unix_inq_len(struct sock *sk);

include/uapi/linux/landlock.h

@@ -12,31 +12,44 @@
 #include <linux/types.h>
 
 /**
- * struct landlock_ruleset_attr - Ruleset definition
+ * struct landlock_ruleset_attr - Ruleset definition.
  *
- * Argument of sys_landlock_create_ruleset().  This structure can grow in
- * future versions.
+ * Argument of sys_landlock_create_ruleset().
+ *
+ * This structure defines a set of *handled access rights*, a set of actions on
+ * different object types, which should be denied by default when the ruleset is
+ * enacted.  Vice versa, access rights that are not specifically listed here are
+ * not going to be denied by this ruleset when it is enacted.
+ *
+ * For historical reasons, the %LANDLOCK_ACCESS_FS_REFER right is always denied
+ * by default, even when its bit is not set in @handled_access_fs.  In order to
+ * add new rules with this access right, the bit must still be set explicitly
+ * (cf. `Filesystem flags`_).
+ *
+ * The explicit listing of *handled access rights* is required for backwards
+ * compatibility reasons.  In most use cases, processes that use Landlock will
+ * *handle* a wide range or all access rights that they know about at build time
+ * (and that they have tested with a kernel that supported them all).
+ *
+ * This structure can grow in future Landlock versions.
  */
 struct landlock_ruleset_attr {
 	/**
-	 * @handled_access_fs: Bitmask of actions (cf. `Filesystem flags`_)
-	 * that is handled by this ruleset and should then be forbidden if no
-	 * rule explicitly allow them: it is a deny-by-default list that should
-	 * contain as much Landlock access rights as possible. Indeed, all
-	 * Landlock filesystem access rights that are not part of
-	 * handled_access_fs are allowed.  This is needed for backward
-	 * compatibility reasons.  One exception is the
-	 * %LANDLOCK_ACCESS_FS_REFER access right, which is always implicitly
-	 * handled, but must still be explicitly handled to add new rules with
-	 * this access right.
+	 * @handled_access_fs: Bitmask of handled filesystem actions
+	 * (cf. `Filesystem flags`_).
 	 */
 	__u64 handled_access_fs;
 	/**
-	 * @handled_access_net: Bitmask of actions (cf. `Network flags`_)
-	 * that is handled by this ruleset and should then be forbidden if no
-	 * rule explicitly allow them.
+	 * @handled_access_net: Bitmask of handled network actions (cf. `Network
+	 * flags`_).
 	 */
 	__u64 handled_access_net;
+	/**
+	 * @scoped: Bitmask of scopes (cf. `Scope flags`_)
+	 * restricting a Landlock domain from accessing outside
+	 * resources (e.g. IPCs).
+	 */
+	__u64 scoped;
 };
 
 /*
@@ -97,20 +110,21 @@ struct landlock_path_beneath_attr {
  */
 struct landlock_net_port_attr {
 	/**
-	 * @allowed_access: Bitmask of allowed access network for a port
+	 * @allowed_access: Bitmask of allowed network actions for a port
 	 * (cf. `Network flags`_).
 	 */
 	__u64 allowed_access;
 	/**
 	 * @port: Network port in host endianness.
 	 *
-	 * It should be noted that port 0 passed to :manpage:`bind(2)` will
-	 * bind to an available port from a specific port range. This can be
-	 * configured thanks to the ``/proc/sys/net/ipv4/ip_local_port_range``
-	 * sysctl (also used for IPv6). A Landlock rule with port 0 and the
-	 * ``LANDLOCK_ACCESS_NET_BIND_TCP`` right means that requesting to bind
-	 * on port 0 is allowed and it will automatically translate to binding
-	 * on the related port range.
+	 * It should be noted that port 0 passed to :manpage:`bind(2)` will bind
+	 * to an available port from the ephemeral port range.  This can be
+	 * configured with the ``/proc/sys/net/ipv4/ip_local_port_range`` sysctl
+	 * (also used for IPv6).
+	 *
+	 * A Landlock rule with port 0 and the ``LANDLOCK_ACCESS_NET_BIND_TCP``
+	 * right means that requesting to bind on port 0 is allowed and it will
+	 * automatically translate to binding on the related port range.
 	 */
 	__u64 port;
 };
@@ -131,10 +145,10 @@ struct landlock_net_port_attr {
  * The following access rights apply only to files:
  *
  * - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file.
- * - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. Note that
- *   you might additionally need the %LANDLOCK_ACCESS_FS_TRUNCATE right in order
- *   to overwrite files with :manpage:`open(2)` using ``O_TRUNC`` or
- *   :manpage:`creat(2)`.
+ * - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access.  When
+ *   opening files for writing, you will often additionally need the
+ *   %LANDLOCK_ACCESS_FS_TRUNCATE right.  In many cases, these system calls
+ *   truncate existing files when overwriting them (e.g., :manpage:`creat(2)`).
  * - %LANDLOCK_ACCESS_FS_READ_FILE: Open a file with read access.
  * - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file with :manpage:`truncate(2)`,
  *   :manpage:`ftruncate(2)`, :manpage:`creat(2)`, or :manpage:`open(2)` with
@@ -256,7 +270,7 @@ struct landlock_net_port_attr {
  * These flags enable to restrict a sandboxed process to a set of network
  * actions. This is supported since the Landlock ABI version 4.
  *
- * TCP sockets with allowed actions:
+ * The following access rights apply to TCP port numbers:
  *
  * - %LANDLOCK_ACCESS_NET_BIND_TCP: Bind a TCP socket to a local port.
  * - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect an active TCP socket to
@@ -266,4 +280,25 @@ struct landlock_net_port_attr {
 #define LANDLOCK_ACCESS_NET_BIND_TCP			(1ULL << 0)
 #define LANDLOCK_ACCESS_NET_CONNECT_TCP			(1ULL << 1)
 /* clang-format on */
+
+/**
+ * DOC: scope
+ *
+ * Scope flags
+ * ~~~~~~~~~~~
+ *
+ * These flags enable to isolate a sandboxed process from a set of IPC actions.
+ * Setting a flag for a ruleset will isolate the Landlock domain to forbid
+ * connections to resources outside the domain.
+ *
+ * Scopes:
+ *
+ * - %LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET: Restrict a sandboxed process from
+ *   connecting to an abstract UNIX socket created by a process outside the
+ *   related Landlock domain (e.g. a parent domain or a non-sandboxed process).
+ */
+/* clang-format off */
+#define LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET		(1ULL << 0)
+/* clang-format on*/
+
 #endif /* _UAPI_LINUX_LANDLOCK_H */

net/core/skmsg.c

@@ -833,6 +833,8 @@ static void sk_psock_destroy(struct work_struct *work)
 
 	if (psock->sk_redir)
 		sock_put(psock->sk_redir);
+	if (psock->sk_pair)
+		sock_put(psock->sk_pair);
 	sock_put(psock->sk);
 	kfree(psock);
 }

net/unix/af_unix.c

@@ -205,8 +205,6 @@ static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb)
 }
 #endif /* CONFIG_SECURITY_NETWORK */
 
-#define unix_peer(sk) (unix_sk(sk)->peer)
-
 static inline int unix_our_peer(struct sock *sk, struct sock *osk)
 {
 	return unix_peer(osk) == sk;

net/unix/unix_bpf.c

@@ -160,12 +160,17 @@ int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool re
 
 int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
 {
+	struct sock *sk_pair;
+
 	if (restore) {
 		sk->sk_write_space = psock->saved_write_space;
 		sock_replace_proto(sk, psock->sk_proto);
 		return 0;
 	}
 
+	sk_pair = unix_peer(sk);
+	sock_hold(sk_pair);
+	psock->sk_pair = sk_pair;
 	unix_stream_bpf_check_needs_rebuild(psock->sk_proto);
 	sock_replace_proto(sk, &unix_stream_bpf_prot);
 	return 0;