* [PATCH v4 1/7] landlock: Add UDP bind() access control
2026-05-02 12:42 [PATCH v4 0/7] landlock: Add UDP access control support Matthieu Buffet
@ 2026-05-02 12:43 ` Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 2/7] landlock: Add UDP connect() " Matthieu Buffet
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Matthieu Buffet @ 2026-05-02 12:43 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Günther Noack, linux-security-module, Mikhail Ivanov,
konstantin.meskhidze, Tingmao Wang, netdev, Matthieu Buffet
Add support for a first fine-grained UDP access right.
LANDLOCK_ACCESS_NET_BIND_UDP controls the ability to set the local port
of a UDP socket (via bind()). It will be useful for servers (to start
receiving datagrams), and for some clients that need to use a specific
source port (e.g. mDNS requires to use port 5353)
For obvious performance concerns, access control is only enforced when
configuring sockets, not when using them for common send/recv
operations.
Bump ABI to allow userspace to detect and use this new right.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
---
include/uapi/linux/landlock.h | 12 +++++++++---
security/landlock/audit.c | 1 +
security/landlock/limits.h | 2 +-
security/landlock/net.c | 18 ++++++++++++------
security/landlock/syscalls.c | 2 +-
tools/testing/selftests/landlock/base_test.c | 4 ++--
tools/testing/selftests/landlock/net_test.c | 5 +++--
7 files changed, 29 insertions(+), 15 deletions(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 10a346e55e95..045b251ff1b4 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -201,9 +201,9 @@ struct landlock_net_port_attr {
* with ``setsockopt(IP_LOCAL_PORT_RANGE)``.
*
* 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 a kernel-assigned ephemeral
- * port.
+ * or %LANDLOCK_ACCESS_NET_BIND_UDP right means that requesting to bind
+ * on port 0 is allowed and it will automatically translate to binding
+ * on a kernel-assigned ephemeral port.
*/
__u64 port;
};
@@ -373,10 +373,16 @@ struct landlock_net_port_attr {
* port. Support added in Landlock ABI version 4.
* - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect TCP sockets to the given
* remote port. Support added in Landlock ABI version 4.
+ *
+ * And similarly for UDP port numbers:
+ *
+ * - %LANDLOCK_ACCESS_NET_BIND_UDP: Bind UDP sockets to the given local
+ * port. Support added in Landlock ABI version 10.
*/
/* clang-format off */
#define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0)
#define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1)
+#define LANDLOCK_ACCESS_NET_BIND_UDP (1ULL << 2)
/* clang-format on */
/**
diff --git a/security/landlock/audit.c b/security/landlock/audit.c
index 8d0edf94037d..e676ebffeebe 100644
--- a/security/landlock/audit.c
+++ b/security/landlock/audit.c
@@ -45,6 +45,7 @@ static_assert(ARRAY_SIZE(fs_access_strings) == LANDLOCK_NUM_ACCESS_FS);
static const char *const net_access_strings[] = {
[BIT_INDEX(LANDLOCK_ACCESS_NET_BIND_TCP)] = "net.bind_tcp",
[BIT_INDEX(LANDLOCK_ACCESS_NET_CONNECT_TCP)] = "net.connect_tcp",
+ [BIT_INDEX(LANDLOCK_ACCESS_NET_BIND_UDP)] = "net.bind_udp",
};
static_assert(ARRAY_SIZE(net_access_strings) == LANDLOCK_NUM_ACCESS_NET);
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index b454ad73b15e..c0f30a4591b8 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -23,7 +23,7 @@
#define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
#define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
-#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_CONNECT_TCP
+#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_BIND_UDP
#define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
#define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET)
diff --git a/security/landlock/net.c b/security/landlock/net.c
index c368649985c5..f9ccb52e7d45 100644
--- a/security/landlock/net.c
+++ b/security/landlock/net.c
@@ -81,15 +81,17 @@ static int current_check_access_socket(struct socket *const sock,
* inconsistencies and return -EINVAL if needed.
*/
return 0;
- } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
+ } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP ||
+ access_request == LANDLOCK_ACCESS_NET_BIND_UDP) {
/*
* Binding to an AF_UNSPEC address is treated
* differently by IPv4 and IPv6 sockets. The socket's
* family may change under our feet due to
* setsockopt(IPV6_ADDRFORM), but that's ok: we either
- * reject entirely or require
- * %LANDLOCK_ACCESS_NET_BIND_TCP for the given port, so
- * it cannot be used to bypass the policy.
+ * reject entirely for IPv6 or require
+ * %LANDLOCK_ACCESS_NET_BIND_TCP or
+ * %LANDLOCK_ACCESS_NET_BIND_UDP for IPv4,
+ * so it cannot be used to bypass the policy.
*
* IPv4 sockets map AF_UNSPEC to AF_INET for
* retrocompatibility for bind accesses, only if the
@@ -135,7 +137,8 @@ static int current_check_access_socket(struct socket *const sock,
if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
audit_net.dport = port;
audit_net.v4info.daddr = addr4->sin_addr.s_addr;
- } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
+ } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP ||
+ access_request == LANDLOCK_ACCESS_NET_BIND_UDP) {
audit_net.sport = port;
audit_net.v4info.saddr = addr4->sin_addr.s_addr;
} else {
@@ -157,7 +160,8 @@ static int current_check_access_socket(struct socket *const sock,
if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
audit_net.dport = port;
audit_net.v6info.daddr = addr6->sin6_addr;
- } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
+ } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP ||
+ access_request == LANDLOCK_ACCESS_NET_BIND_UDP) {
audit_net.sport = port;
audit_net.v6info.saddr = addr6->sin6_addr;
} else {
@@ -216,6 +220,8 @@ static int hook_socket_bind(struct socket *const sock,
if (sk_is_tcp(sock->sk))
access_request = LANDLOCK_ACCESS_NET_BIND_TCP;
+ else if (sk_is_udp(sock->sk))
+ access_request = LANDLOCK_ACCESS_NET_BIND_UDP;
else
return 0;
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index accfd2e5a0cd..d45469d5d464 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -166,7 +166,7 @@ static const struct file_operations ruleset_fops = {
* If the change involves a fix that requires userspace awareness, also update
* the errata documentation in Documentation/userspace-api/landlock.rst .
*/
-const int landlock_abi_version = 9;
+const int landlock_abi_version = 10;
/**
* sys_landlock_create_ruleset - Create a new ruleset
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 30d37234086c..6c8113c2ded1 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -76,8 +76,8 @@ TEST(abi_version)
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
};
- ASSERT_EQ(9, landlock_create_ruleset(NULL, 0,
- LANDLOCK_CREATE_RULESET_VERSION));
+ ASSERT_EQ(10, landlock_create_ruleset(NULL, 0,
+ LANDLOCK_CREATE_RULESET_VERSION));
ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
LANDLOCK_CREATE_RULESET_VERSION));
diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
index 4c528154ea92..ec392d971ea3 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -1326,11 +1326,12 @@ FIXTURE_TEARDOWN(mini)
/* clang-format off */
-#define ACCESS_LAST LANDLOCK_ACCESS_NET_CONNECT_TCP
+#define ACCESS_LAST LANDLOCK_ACCESS_NET_BIND_UDP
#define ACCESS_ALL ( \
LANDLOCK_ACCESS_NET_BIND_TCP | \
- LANDLOCK_ACCESS_NET_CONNECT_TCP)
+ LANDLOCK_ACCESS_NET_CONNECT_TCP | \
+ LANDLOCK_ACCESS_NET_BIND_UDP)
/* clang-format on */
--
2.39.5
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v4 2/7] landlock: Add UDP connect() access control
2026-05-02 12:42 [PATCH v4 0/7] landlock: Add UDP access control support Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 1/7] landlock: Add UDP bind() access control Matthieu Buffet
@ 2026-05-02 12:43 ` Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 3/7] landlock: Add UDP send " Matthieu Buffet
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Matthieu Buffet @ 2026-05-02 12:43 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Günther Noack, linux-security-module, Mikhail Ivanov,
konstantin.meskhidze, Tingmao Wang, netdev, Matthieu Buffet
Add support for a second fine-grained UDP access right.
This first half of LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP controls the
ability to set the remote port of a socket (via connect()). It will be
useful for applications that send datagrams, and for some servers too
(those creating per-client sockets, which want to receive traffic only
from a specific address).
Similarly as for bind(), this access control is performed when
configuring sockets, not in hot code paths.
Include detection of when autobind is about to be required, and check if
the process would be allowed to call bind(0) explicitly. Autobind can
only be performed when sending a first datagram, when connect()ing, and
in some splice() EOF edge case which, afaiu, can only happen after a
remote peer has been set (which is already covered).
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
---
include/uapi/linux/landlock.h | 19 +++++
security/landlock/audit.c | 2 +
security/landlock/limits.h | 2 +-
security/landlock/net.c | 79 +++++++++++++++++----
tools/testing/selftests/landlock/net_test.c | 5 +-
5 files changed, 92 insertions(+), 15 deletions(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 045b251ff1b4..22c8cc63f30e 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -378,11 +378,30 @@ struct landlock_net_port_attr {
*
* - %LANDLOCK_ACCESS_NET_BIND_UDP: Bind UDP sockets to the given local
* port. Support added in Landlock ABI version 10.
+ * - %LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP: Set the remote port of UDP
+ * sockets to the given port, or send datagrams to the given remote port
+ * ignoring any destination pre-set on a socket. Support added in
+ * Landlock ABI version 10.
+ *
+ * .. note:: Setting a remote address or sending a first datagram
+ * auto-binds UDP sockets to an ephemeral local source port if not
+ * already bound. To allow this if both %LANDLOCK_ACCESS_NET_BIND_UDP
+ * and %LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP are handled, you need to
+ * either:
+ *
+ * - use a socket already bound to a port before the ruleset started
+ * being enforced;
+ * - or grant %LANDLOCK_ACCESS_NET_BIND_UDP on port 0, meaning "any
+ * port in the ephemeral port range";
+ * - or grant %LANDLOCK_ACCESS_NET_BIND_UDP on a specific port, and
+ * call :manpage:`bind(2)` on that port before trying to
+ * :manpage:`connect(2)` or send datagrams.
*/
/* clang-format off */
#define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0)
#define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1)
#define LANDLOCK_ACCESS_NET_BIND_UDP (1ULL << 2)
+#define LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP (1ULL << 3)
/* clang-format on */
/**
diff --git a/security/landlock/audit.c b/security/landlock/audit.c
index e676ebffeebe..851647197a01 100644
--- a/security/landlock/audit.c
+++ b/security/landlock/audit.c
@@ -46,6 +46,8 @@ static const char *const net_access_strings[] = {
[BIT_INDEX(LANDLOCK_ACCESS_NET_BIND_TCP)] = "net.bind_tcp",
[BIT_INDEX(LANDLOCK_ACCESS_NET_CONNECT_TCP)] = "net.connect_tcp",
[BIT_INDEX(LANDLOCK_ACCESS_NET_BIND_UDP)] = "net.bind_udp",
+ [BIT_INDEX(LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP)] =
+ "net.connect_send_udp",
};
static_assert(ARRAY_SIZE(net_access_strings) == LANDLOCK_NUM_ACCESS_NET);
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index c0f30a4591b8..a4d908b240a2 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -23,7 +23,7 @@
#define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
#define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
-#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_BIND_UDP
+#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP
#define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
#define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET)
diff --git a/security/landlock/net.c b/security/landlock/net.c
index f9ccb52e7d45..045881f81295 100644
--- a/security/landlock/net.c
+++ b/security/landlock/net.c
@@ -68,16 +68,17 @@ static int current_check_access_socket(struct socket *const sock,
switch (address->sa_family) {
case AF_UNSPEC:
- if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
+ if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP ||
+ access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) {
/*
* Connecting to an address with AF_UNSPEC dissolves
- * the TCP association, which have the same effect as
- * closing the connection while retaining the socket
- * object (i.e., the file descriptor). As for dropping
- * privileges, closing connections is always allowed.
- *
- * For a TCP access control system, this request is
- * legitimate. Let the network stack handle potential
+ * the remote association while retaining the socket
+ * object (i.e., the file descriptor). For TCP, it has
+ * the same effect as closing the connection. For UDP,
+ * it removes any preset remote address. As for
+ * dropping privileges, these actions are always
+ * allowed.
+ * Let the network stack handle potential
* inconsistencies and return -EINVAL if needed.
*/
return 0;
@@ -134,7 +135,8 @@ static int current_check_access_socket(struct socket *const sock,
addr4 = (struct sockaddr_in *)address;
port = addr4->sin_port;
- if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
+ if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP ||
+ access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) {
audit_net.dport = port;
audit_net.v4info.daddr = addr4->sin_addr.s_addr;
} else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP ||
@@ -157,7 +159,8 @@ static int current_check_access_socket(struct socket *const sock,
addr6 = (struct sockaddr_in6 *)address;
port = addr6->sin6_port;
- if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
+ if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP ||
+ access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) {
audit_net.dport = port;
audit_net.v6info.daddr = addr6->sin6_addr;
} else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP ||
@@ -213,6 +216,50 @@ static int current_check_access_socket(struct socket *const sock,
return -EACCES;
}
+static int current_check_autobind_udp_socket(struct socket *const sock)
+{
+ struct sockaddr_storage port0 = { 0 };
+
+ /*
+ * On UDP sockets, if a local port has not already been bound,
+ * calling connect() or sending a first datagram has the side
+ * effect of autobinding an ephemeral port: we also have to check
+ * that the process would have had the right to bind(0) explicitly.
+ * Note: socket is not locked, so another thread could do an
+ * explicit bind(!=0) on this socket, changing inet_num to non-zero
+ * after we read it, but this would only have us enforce an
+ * additional bind(0) access check and would not bypass policy.
+ */
+ if (inet_sk(sock->sk)->inet_num != 0)
+ return 0;
+
+ /*
+ * Construct a struct sockaddr* with port 0 to pretend the
+ * process tried to bind() on that address.
+ */
+ port0.ss_family = sock->sk->__sk_common.skc_family;
+ switch (port0.ss_family) {
+ case AF_INET: {
+ ((struct sockaddr_in *)&port0)->sin_port = 0;
+ break;
+ }
+
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6: {
+ ((struct sockaddr_in6 *)&port0)->sin6_port = 0;
+ break;
+ }
+#endif /* IS_ENABLED(CONFIG_IPV6) */
+
+ default:
+ return 0;
+ }
+
+ return current_check_access_socket(sock, (struct sockaddr *)&port0,
+ sizeof(port0),
+ LANDLOCK_ACCESS_NET_BIND_UDP);
+}
+
static int hook_socket_bind(struct socket *const sock,
struct sockaddr *const address, const int addrlen)
{
@@ -234,14 +281,22 @@ static int hook_socket_connect(struct socket *const sock,
const int addrlen)
{
access_mask_t access_request;
+ int ret = 0;
if (sk_is_tcp(sock->sk))
access_request = LANDLOCK_ACCESS_NET_CONNECT_TCP;
+ else if (sk_is_udp(sock->sk))
+ access_request = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP;
else
return 0;
- return current_check_access_socket(sock, address, addrlen,
- access_request);
+ ret = current_check_access_socket(sock, address, addrlen,
+ access_request);
+
+ if (ret == 0 && sk_is_udp(sock->sk))
+ ret = current_check_autobind_udp_socket(sock);
+
+ return ret;
}
static struct security_hook_list landlock_hooks[] __ro_after_init = {
diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
index ec392d971ea3..016c7277e370 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -1326,12 +1326,13 @@ FIXTURE_TEARDOWN(mini)
/* clang-format off */
-#define ACCESS_LAST LANDLOCK_ACCESS_NET_BIND_UDP
+#define ACCESS_LAST LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP
#define ACCESS_ALL ( \
LANDLOCK_ACCESS_NET_BIND_TCP | \
LANDLOCK_ACCESS_NET_CONNECT_TCP | \
- LANDLOCK_ACCESS_NET_BIND_UDP)
+ LANDLOCK_ACCESS_NET_BIND_UDP | \
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP)
/* clang-format on */
--
2.39.5
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v4 3/7] landlock: Add UDP send access control
2026-05-02 12:42 [PATCH v4 0/7] landlock: Add UDP access control support Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 1/7] landlock: Add UDP bind() access control Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 2/7] landlock: Add UDP connect() " Matthieu Buffet
@ 2026-05-02 12:43 ` Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 4/7] selftests/landlock: Add UDP bind/connect tests Matthieu Buffet
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Matthieu Buffet @ 2026-05-02 12:43 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Günther Noack, linux-security-module, Mikhail Ivanov,
konstantin.meskhidze, Tingmao Wang, netdev, Matthieu Buffet
Add the second half of LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP: control the
ability to specify an explicit destination when sending a datagram, to
override any remote peer set on a UDP socket (in sendto(), sendmsg(), and
sendmmsg()). It will make the right useful for clients which want to
send datagrams while specifying a destination address each time.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
---
include/uapi/linux/landlock.h | 4 ++
security/landlock/net.c | 70 ++++++++++++++++++++++++++++++++---
2 files changed, 68 insertions(+), 6 deletions(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 22c8cc63f30e..b147223efc97 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -396,6 +396,10 @@ struct landlock_net_port_attr {
* - or grant %LANDLOCK_ACCESS_NET_BIND_UDP on a specific port, and
* call :manpage:`bind(2)` on that port before trying to
* :manpage:`connect(2)` or send datagrams.
+ *
+ * .. note:: Sending datagrams to an ``AF_UNSPEC`` destination address
+ * family is not supported for IPv6 UDP sockets: you will need to use a
+ * ``NULL`` address instead.
*/
/* clang-format off */
#define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0)
diff --git a/security/landlock/net.c b/security/landlock/net.c
index 045881f81295..8a53aebdb8c6 100644
--- a/security/landlock/net.c
+++ b/security/landlock/net.c
@@ -44,7 +44,8 @@ int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
static int current_check_access_socket(struct socket *const sock,
struct sockaddr *const address,
const int addrlen,
- access_mask_t access_request)
+ access_mask_t access_request,
+ bool connecting)
{
__be16 port;
struct layer_access_masks layer_masks = {};
@@ -69,7 +70,8 @@ static int current_check_access_socket(struct socket *const sock,
switch (address->sa_family) {
case AF_UNSPEC:
if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP ||
- access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) {
+ (access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP &&
+ connecting)) {
/*
* Connecting to an address with AF_UNSPEC dissolves
* the remote association while retaining the socket
@@ -82,6 +84,35 @@ static int current_check_access_socket(struct socket *const sock,
* inconsistencies and return -EINVAL if needed.
*/
return 0;
+ } else if (access_request ==
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) {
+ if (sock->sk->__sk_common.skc_family == AF_INET6) {
+ /*
+ * We cannot allow sending UDP datagrams to an
+ * explicit AF_UNSPEC address on IPv6 sockets,
+ * even if AF_UNSPEC is treated as "no address"
+ * on such sockets (so it should always be allowed).
+ * That's because the socket's family can change under
+ * our feet (if another thread calls setsockopt(IPV6_ADDRFORM))
+ * to IPv4, which would then treat AF_UNSPEC as
+ * AF_INET.
+ */
+ audit_net.family = AF_UNSPEC;
+ landlock_init_layer_masks(
+ subject->domain, access_request,
+ &layer_masks, LANDLOCK_KEY_NET_PORT);
+ landlock_log_denial(
+ subject,
+ &(struct landlock_request){
+ .type = LANDLOCK_REQUEST_NET_ACCESS,
+ .audit.type =
+ LSM_AUDIT_DATA_NET,
+ .audit.u.net = &audit_net,
+ .access = access_request,
+ .layer_masks = &layer_masks,
+ });
+ return -EACCES;
+ }
} else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP ||
access_request == LANDLOCK_ACCESS_NET_BIND_UDP) {
/*
@@ -124,7 +155,10 @@ static int current_check_access_socket(struct socket *const sock,
} else {
WARN_ON_ONCE(1);
}
- /* Only for bind(AF_UNSPEC+INADDR_ANY) on IPv4 socket. */
+ /*
+ * For bind(AF_UNSPEC+INADDR_ANY) on IPv4 socket and
+ * for sending to AF_UNSPEC addresses on IPv4 socket.
+ */
fallthrough;
case AF_INET: {
const struct sockaddr_in *addr4;
@@ -257,7 +291,7 @@ static int current_check_autobind_udp_socket(struct socket *const sock)
return current_check_access_socket(sock, (struct sockaddr *)&port0,
sizeof(port0),
- LANDLOCK_ACCESS_NET_BIND_UDP);
+ LANDLOCK_ACCESS_NET_BIND_UDP, false);
}
static int hook_socket_bind(struct socket *const sock,
@@ -273,7 +307,7 @@ static int hook_socket_bind(struct socket *const sock,
return 0;
return current_check_access_socket(sock, address, addrlen,
- access_request);
+ access_request, false);
}
static int hook_socket_connect(struct socket *const sock,
@@ -291,7 +325,7 @@ static int hook_socket_connect(struct socket *const sock,
return 0;
ret = current_check_access_socket(sock, address, addrlen,
- access_request);
+ access_request, true);
if (ret == 0 && sk_is_udp(sock->sk))
ret = current_check_autobind_udp_socket(sock);
@@ -299,9 +333,33 @@ static int hook_socket_connect(struct socket *const sock,
return ret;
}
+static int hook_socket_sendmsg(struct socket *const sock,
+ struct msghdr *const msg, const int size)
+{
+ struct sockaddr *const address = msg->msg_name;
+ const int addrlen = msg->msg_namelen;
+ access_mask_t access_request;
+ int ret = 0;
+
+ if (sk_is_udp(sock->sk))
+ access_request = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP;
+ else
+ return 0;
+
+ if (address != NULL)
+ ret = current_check_access_socket(sock, address, addrlen,
+ access_request, false);
+
+ if (ret == 0)
+ ret = current_check_autobind_udp_socket(sock);
+
+ return ret;
+}
+
static struct security_hook_list landlock_hooks[] __ro_after_init = {
LSM_HOOK_INIT(socket_bind, hook_socket_bind),
LSM_HOOK_INIT(socket_connect, hook_socket_connect),
+ LSM_HOOK_INIT(socket_sendmsg, hook_socket_sendmsg),
};
__init void landlock_add_net_hooks(void)
--
2.39.5
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v4 4/7] selftests/landlock: Add UDP bind/connect tests
2026-05-02 12:42 [PATCH v4 0/7] landlock: Add UDP access control support Matthieu Buffet
` (2 preceding siblings ...)
2026-05-02 12:43 ` [PATCH v4 3/7] landlock: Add UDP send " Matthieu Buffet
@ 2026-05-02 12:43 ` Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 5/7] selftests/landlock: Add tests for sendmsg() Matthieu Buffet
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Matthieu Buffet @ 2026-05-02 12:43 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Günther Noack, linux-security-module, Mikhail Ivanov,
konstantin.meskhidze, Tingmao Wang, netdev, Matthieu Buffet
Make basic changes to the existing bind() and connect() test suite to
cover UDP restriction.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
---
tools/testing/selftests/landlock/net_test.c | 488 ++++++++++++++++----
1 file changed, 401 insertions(+), 87 deletions(-)
diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
index 016c7277e370..568a6ed7139c 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -35,6 +35,7 @@ enum sandbox_type {
NO_SANDBOX,
/* This may be used to test rules that allow *and* deny accesses. */
TCP_SANDBOX,
+ UDP_SANDBOX,
};
static int set_service(struct service_fixture *const srv,
@@ -93,23 +94,53 @@ static bool prot_is_tcp(const struct protocol_variant *const prot)
(prot->protocol == IPPROTO_TCP || prot->protocol == IPPROTO_IP);
}
+static bool prot_is_udp(const struct protocol_variant *const prot)
+{
+ return (prot->domain == AF_INET || prot->domain == AF_INET6) &&
+ prot->type == SOCK_DGRAM &&
+ (prot->protocol == IPPROTO_UDP || prot->protocol == IPPROTO_IP);
+}
+
static bool is_restricted(const struct protocol_variant *const prot,
const enum sandbox_type sandbox)
{
if (sandbox == TCP_SANDBOX)
return prot_is_tcp(prot);
+ else if (sandbox == UDP_SANDBOX)
+ return prot_is_udp(prot);
return false;
}
static int socket_variant(const struct service_fixture *const srv)
{
+ /* Arbitrary value just to not block other tests indefinitely. */
+ const struct timeval timeout = {
+ .tv_sec = 0,
+ .tv_usec = 100000,
+ };
+ int sockfd;
int ret;
- ret = socket(srv->protocol.domain, srv->protocol.type | SOCK_CLOEXEC,
- srv->protocol.protocol);
- if (ret < 0)
+ sockfd = socket(srv->protocol.domain, srv->protocol.type | SOCK_CLOEXEC,
+ srv->protocol.protocol);
+ if (sockfd < 0)
return -errno;
- return ret;
+
+ ret = setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &timeout,
+ sizeof(timeout));
+ if (ret != 0) {
+ ret = -errno;
+ close(sockfd);
+ return ret;
+ }
+ ret = setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, &timeout,
+ sizeof(timeout));
+ if (ret != 0) {
+ ret = -errno;
+ close(sockfd);
+ return ret;
+ }
+ return sockfd;
}
#ifndef SIN6_LEN_RFC2133
@@ -271,10 +302,9 @@ FIXTURE_VARIANT(protocol)
FIXTURE_SETUP(protocol)
{
- const struct protocol_variant prot_unspec = {
- .domain = AF_UNSPEC,
- .type = SOCK_STREAM,
- };
+ struct protocol_variant prot_unspec = variant->prot;
+
+ prot_unspec.domain = AF_UNSPEC;
disable_caps(_metadata);
@@ -510,6 +540,92 @@ FIXTURE_VARIANT_ADD(protocol, tcp_sandbox_with_unix_datagram) {
},
};
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_ipv4_udp1) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET,
+ .type = SOCK_DGRAM,
+ .protocol = IPPROTO_UDP,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_ipv4_udp2) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET,
+ .type = SOCK_DGRAM,
+ /* IPPROTO_IP == 0 */
+ .protocol = IPPROTO_IP,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_ipv6_udp1) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET6,
+ .type = SOCK_DGRAM,
+ .protocol = IPPROTO_UDP,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_ipv6_udp2) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET6,
+ .type = SOCK_DGRAM,
+ /* IPPROTO_IP == 0 */
+ .protocol = IPPROTO_IP,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_ipv4_tcp) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET,
+ .type = SOCK_STREAM,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_ipv6_tcp) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET6,
+ .type = SOCK_STREAM,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_unix_stream) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_UNIX,
+ .type = SOCK_STREAM,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(protocol, udp_sandbox_with_unix_datagram) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_UNIX,
+ .type = SOCK_DGRAM,
+ },
+};
+
static void test_bind_and_connect(struct __test_metadata *const _metadata,
const struct service_fixture *const srv,
const bool deny_bind, const bool deny_connect)
@@ -602,7 +718,7 @@ static void test_bind_and_connect(struct __test_metadata *const _metadata,
ret = connect_variant(connect_fd, srv);
if (deny_connect) {
EXPECT_EQ(-EACCES, ret);
- } else if (deny_bind) {
+ } else if (deny_bind && srv->protocol.type == SOCK_STREAM) {
/* No listening server. */
EXPECT_EQ(-ECONNREFUSED, ret);
} else {
@@ -641,18 +757,25 @@ static void test_bind_and_connect(struct __test_metadata *const _metadata,
TEST_F(protocol, bind)
{
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
+ const __u64 bind_access =
+ (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_BIND_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP);
+ const __u64 conn_access =
+ (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_CONNECT_TCP :
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .handled_access_net = bind_access | conn_access,
};
- const struct landlock_net_port_attr tcp_bind_connect_p0 = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ const struct landlock_net_port_attr bind_connect_p0 = {
+ .allowed_access = bind_access | conn_access,
.port = self->srv0.port,
};
- const struct landlock_net_port_attr tcp_connect_p1 = {
- .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ const struct landlock_net_port_attr connect_p1 = {
+ .allowed_access = conn_access,
.port = self->srv1.port,
};
int ruleset_fd;
@@ -664,12 +787,26 @@ TEST_F(protocol, bind)
/* Allows connect and bind for the first port. */
ASSERT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_bind_connect_p0, 0));
+ &bind_connect_p0, 0));
/* Allows connect and denies bind for the second port. */
ASSERT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_connect_p1, 0));
+ &connect_p1, 0));
+
+ /*
+ * For UDP sockets, allows binding to ephemeral ports
+ * (required to connect or send a first datagram)
+ */
+ if (variant->sandbox == UDP_SANDBOX) {
+ const struct landlock_net_port_attr bind_ephemeral = {
+ .allowed_access = bind_access,
+ .port = 0,
+ };
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
+ LANDLOCK_RULE_NET_PORT,
+ &bind_ephemeral, 0));
+ }
enforce_ruleset(_metadata, ruleset_fd);
EXPECT_EQ(0, close(ruleset_fd));
@@ -691,18 +828,25 @@ TEST_F(protocol, bind)
TEST_F(protocol, connect)
{
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
+ const __u64 bind_access =
+ (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_BIND_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP);
+ const __u64 conn_access =
+ (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_CONNECT_TCP :
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .handled_access_net = bind_access | conn_access,
};
- const struct landlock_net_port_attr tcp_bind_connect_p0 = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ const struct landlock_net_port_attr bind_connect_p0 = {
+ .allowed_access = bind_access | conn_access,
.port = self->srv0.port,
};
- const struct landlock_net_port_attr tcp_bind_p1 = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
+ const struct landlock_net_port_attr bind_p1 = {
+ .allowed_access = bind_access,
.port = self->srv1.port,
};
int ruleset_fd;
@@ -714,12 +858,26 @@ TEST_F(protocol, connect)
/* Allows connect and bind for the first port. */
ASSERT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_bind_connect_p0, 0));
+ &bind_connect_p0, 0));
/* Allows bind and denies connect for the second port. */
ASSERT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_bind_p1, 0));
+ &bind_p1, 0));
+
+ /*
+ * For UDP sockets, allows binding to ephemeral ports
+ * (required to connect or send a first datagram)
+ */
+ if (variant->sandbox == UDP_SANDBOX) {
+ const struct landlock_net_port_attr bind_ephemeral = {
+ .allowed_access = bind_access,
+ .port = 0,
+ };
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
+ LANDLOCK_RULE_NET_PORT,
+ &bind_ephemeral, 0));
+ }
enforce_ruleset(_metadata, ruleset_fd);
EXPECT_EQ(0, close(ruleset_fd));
@@ -737,16 +895,20 @@ TEST_F(protocol, connect)
TEST_F(protocol, bind_unspec)
{
+ const int bind_access = (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_BIND_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP);
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP,
+ .handled_access_net = bind_access,
};
- const struct landlock_net_port_attr tcp_bind = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
+ const struct landlock_net_port_attr rule_bind = {
+ .allowed_access = bind_access,
.port = self->srv0.port,
};
int bind_fd, ret;
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
const int ruleset_fd = landlock_create_ruleset(
&ruleset_attr, sizeof(ruleset_attr), 0);
ASSERT_LE(0, ruleset_fd);
@@ -754,7 +916,7 @@ TEST_F(protocol, bind_unspec)
/* Allows bind. */
ASSERT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_bind, 0));
+ &rule_bind, 0));
enforce_ruleset(_metadata, ruleset_fd);
EXPECT_EQ(0, close(ruleset_fd));
}
@@ -782,7 +944,8 @@ TEST_F(protocol, bind_unspec)
}
EXPECT_EQ(0, close(bind_fd));
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
const int ruleset_fd = landlock_create_ruleset(
&ruleset_attr, sizeof(ruleset_attr), 0);
ASSERT_LE(0, ruleset_fd);
@@ -828,11 +991,15 @@ TEST_F(protocol, bind_unspec)
TEST_F(protocol, connect_unspec)
{
+ const __u64 connect_right =
+ (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_CONNECT_TCP :
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .handled_access_net = connect_right,
};
- const struct landlock_net_port_attr tcp_connect = {
- .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ const struct landlock_net_port_attr rule_connect = {
+ .allowed_access = connect_right,
.port = self->srv0.port,
};
int bind_fd, client_fd, status;
@@ -865,7 +1032,8 @@ TEST_F(protocol, connect_unspec)
EXPECT_EQ(0, ret);
}
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
const int ruleset_fd = landlock_create_ruleset(
&ruleset_attr, sizeof(ruleset_attr), 0);
ASSERT_LE(0, ruleset_fd);
@@ -873,7 +1041,7 @@ TEST_F(protocol, connect_unspec)
/* Allows connect. */
ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
LANDLOCK_RULE_NET_PORT,
- &tcp_connect, 0));
+ &rule_connect, 0));
enforce_ruleset(_metadata, ruleset_fd);
EXPECT_EQ(0, close(ruleset_fd));
}
@@ -896,7 +1064,8 @@ TEST_F(protocol, connect_unspec)
EXPECT_EQ(0, ret);
}
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
const int ruleset_fd = landlock_create_ruleset(
&ruleset_attr, sizeof(ruleset_attr), 0);
ASSERT_LE(0, ruleset_fd);
@@ -975,6 +1144,13 @@ FIXTURE_VARIANT_ADD(ipv4, tcp_sandbox_with_tcp) {
.type = SOCK_STREAM,
};
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ipv4, udp_sandbox_with_tcp) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .type = SOCK_STREAM,
+};
+
/* clang-format off */
FIXTURE_VARIANT_ADD(ipv4, no_sandbox_with_udp) {
/* clang-format on */
@@ -989,6 +1165,13 @@ FIXTURE_VARIANT_ADD(ipv4, tcp_sandbox_with_udp) {
.type = SOCK_DGRAM,
};
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ipv4, udp_sandbox_with_udp) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .type = SOCK_DGRAM,
+};
+
FIXTURE_SETUP(ipv4)
{
const struct protocol_variant prot = {
@@ -1012,14 +1195,19 @@ TEST_F(ipv4, from_unix_to_inet)
{
int unix_stream_fd, unix_dgram_fd;
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
+ const int access_rights =
+ (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_BIND_TCP |
+ LANDLOCK_ACCESS_NET_CONNECT_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .handled_access_net = access_rights,
};
const struct landlock_net_port_attr tcp_bind_connect_p0 = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .allowed_access = access_rights,
.port = self->srv0.port,
};
int ruleset_fd;
@@ -1680,6 +1868,7 @@ TEST_F(ipv4_tcp, with_fs)
FIXTURE(port_specific)
{
struct service_fixture srv0;
+ struct service_fixture cli1;
};
FIXTURE_VARIANT(port_specific)
@@ -1699,7 +1888,7 @@ FIXTURE_VARIANT_ADD(port_specific, no_sandbox_with_ipv4) {
};
/* clang-format off */
-FIXTURE_VARIANT_ADD(port_specific, sandbox_with_ipv4) {
+FIXTURE_VARIANT_ADD(port_specific, tcp_sandbox_with_ipv4) {
/* clang-format on */
.sandbox = TCP_SANDBOX,
.prot = {
@@ -1708,6 +1897,16 @@ FIXTURE_VARIANT_ADD(port_specific, sandbox_with_ipv4) {
},
};
+/* clang-format off */
+FIXTURE_VARIANT_ADD(port_specific, udp_sandbox_with_ipv4) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET,
+ .type = SOCK_DGRAM,
+ },
+};
+
/* clang-format off */
FIXTURE_VARIANT_ADD(port_specific, no_sandbox_with_ipv6) {
/* clang-format on */
@@ -1719,7 +1918,7 @@ FIXTURE_VARIANT_ADD(port_specific, no_sandbox_with_ipv6) {
};
/* clang-format off */
-FIXTURE_VARIANT_ADD(port_specific, sandbox_with_ipv6) {
+FIXTURE_VARIANT_ADD(port_specific, tcp_sandbox_with_ipv6) {
/* clang-format on */
.sandbox = TCP_SANDBOX,
.prot = {
@@ -1728,11 +1927,22 @@ FIXTURE_VARIANT_ADD(port_specific, sandbox_with_ipv6) {
},
};
+/* clang-format off */
+FIXTURE_VARIANT_ADD(port_specific, udp_sandbox_with_ipv6) {
+ /* clang-format on */
+ .sandbox = UDP_SANDBOX,
+ .prot = {
+ .domain = AF_INET6,
+ .type = SOCK_DGRAM,
+ },
+};
+
FIXTURE_SETUP(port_specific)
{
disable_caps(_metadata);
ASSERT_EQ(0, set_service(&self->srv0, variant->prot, 0));
+ ASSERT_EQ(0, set_service(&self->cli1, variant->prot, 1));
setup_loopback(_metadata);
};
@@ -1747,14 +1957,19 @@ TEST_F(port_specific, bind_connect_zero)
uint16_t port;
/* Adds a rule layer with bind and connect actions. */
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
+ const int access_rights =
+ (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_BIND_TCP |
+ LANDLOCK_ACCESS_NET_CONNECT_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP
+ .handled_access_net = access_rights,
};
- const struct landlock_net_port_attr tcp_bind_connect_zero = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ const struct landlock_net_port_attr bind_connect_zero = {
+ .allowed_access = access_rights,
.port = 0,
};
int ruleset_fd;
@@ -1766,7 +1981,7 @@ TEST_F(port_specific, bind_connect_zero)
/* Checks zero port value on bind and connect actions. */
EXPECT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_bind_connect_zero, 0));
+ &bind_connect_zero, 0));
enforce_ruleset(_metadata, ruleset_fd);
EXPECT_EQ(0, close(ruleset_fd));
@@ -1787,11 +2002,16 @@ TEST_F(port_specific, bind_connect_zero)
ret = bind_variant(bind_fd, &self->srv0);
EXPECT_EQ(0, ret);
- EXPECT_EQ(0, listen(bind_fd, backlog));
+ if (variant->prot.type == SOCK_STREAM)
+ EXPECT_EQ(0, listen(bind_fd, backlog));
/* Connects on port 0. */
ret = connect_variant(connect_fd, &self->srv0);
- EXPECT_EQ(-ECONNREFUSED, ret);
+ if (variant->prot.type == SOCK_STREAM) {
+ EXPECT_EQ(-ECONNREFUSED, ret);
+ } else {
+ EXPECT_EQ(0, ret);
+ }
/* Sets binded port for both protocol families. */
port = get_binded_port(bind_fd, &variant->prot);
@@ -1815,23 +2035,35 @@ TEST_F(port_specific, bind_connect_1023)
int bind_fd, connect_fd, ret;
/* Adds a rule layer with bind and connect actions. */
- if (variant->sandbox == TCP_SANDBOX) {
+ if (variant->sandbox == TCP_SANDBOX ||
+ variant->sandbox == UDP_SANDBOX) {
+ const int bind_right = (variant->sandbox == TCP_SANDBOX ?
+ LANDLOCK_ACCESS_NET_BIND_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP);
+ const int access_rights =
+ (variant->sandbox == TCP_SANDBOX ?
+ (LANDLOCK_ACCESS_NET_BIND_TCP |
+ LANDLOCK_ACCESS_NET_CONNECT_TCP) :
+ (LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP));
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP
+ .handled_access_net = access_rights,
};
/* A rule with port value less than 1024. */
- const struct landlock_net_port_attr tcp_bind_connect_low_range = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ const struct landlock_net_port_attr bind_connect_low_range = {
+ .allowed_access = access_rights,
.port = 1023,
};
/* A rule with 1024 port. */
- const struct landlock_net_port_attr tcp_bind_connect = {
- .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ const struct landlock_net_port_attr bind_connect = {
+ .allowed_access = access_rights,
.port = 1024,
};
+ /* A rule with cli1's port, to use as source port. */
+ const struct landlock_net_port_attr srcport = {
+ .allowed_access = bind_right,
+ .port = self->cli1.port,
+ };
int ruleset_fd;
ruleset_fd = landlock_create_ruleset(&ruleset_attr,
@@ -1840,10 +2072,15 @@ TEST_F(port_specific, bind_connect_1023)
ASSERT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_bind_connect_low_range, 0));
+ &bind_connect_low_range, 0));
ASSERT_EQ(0,
landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &tcp_bind_connect, 0));
+ &bind_connect, 0));
+ if (variant->sandbox == UDP_SANDBOX) {
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
+ LANDLOCK_RULE_NET_PORT,
+ &srcport, 0));
+ }
enforce_ruleset(_metadata, ruleset_fd);
EXPECT_EQ(0, close(ruleset_fd));
@@ -1867,8 +2104,19 @@ TEST_F(port_specific, bind_connect_1023)
ret = bind_variant(bind_fd, &self->srv0);
clear_cap(_metadata, CAP_NET_BIND_SERVICE);
EXPECT_EQ(0, ret);
- EXPECT_EQ(0, listen(bind_fd, backlog));
+ if (variant->prot.type == SOCK_STREAM)
+ EXPECT_EQ(0, listen(bind_fd, backlog));
+ connect_fd = socket_variant(&self->srv0);
+ ASSERT_LE(0, connect_fd);
+ if (variant->prot.type == SOCK_DGRAM) {
+ /*
+ * We are about to connect(), but bind() is restricted, so for
+ * UDP sockets we need to use cli1's port as source port (the
+ * only one we are allowed to use).
+ */
+ EXPECT_EQ(0, bind_variant(connect_fd, &self->cli1));
+ }
/* Connects on the binded port 1023. */
ret = connect_variant(connect_fd, &self->srv0);
EXPECT_EQ(0, ret);
@@ -1887,7 +2135,10 @@ TEST_F(port_specific, bind_connect_1023)
/* Binds on port 1024. */
ret = bind_variant(bind_fd, &self->srv0);
EXPECT_EQ(0, ret);
- EXPECT_EQ(0, listen(bind_fd, backlog));
+ if (variant->prot.type == SOCK_STREAM)
+ EXPECT_EQ(0, listen(bind_fd, backlog));
+ if (variant->prot.type == SOCK_DGRAM)
+ EXPECT_EQ(0, bind_variant(connect_fd, &self->cli1));
/* Connects on the binded port 1024. */
ret = connect_variant(connect_fd, &self->srv0);
@@ -1897,23 +2148,30 @@ TEST_F(port_specific, bind_connect_1023)
EXPECT_EQ(0, close(bind_fd));
}
-static int matches_log_tcp(const int audit_fd, const char *const blockers,
- const char *const dir_addr, const char *const addr,
- const char *const dir_port)
+static int matches_auditlog(const int audit_fd, const char *const blockers,
+ const char *const dir_addr, const char *const addr,
+ const char *const dir_port)
{
- static const char log_template[] = REGEX_LANDLOCK_PREFIX
+ static const char log_with_addrport_tmpl[] = REGEX_LANDLOCK_PREFIX
" blockers=%s %s=%s %s=1024$";
+ static const char log_without_addrport_tmpl[] = REGEX_LANDLOCK_PREFIX
+ " blockers=%s";
/*
* Max strlen(blockers): 16
* Max strlen(dir_addr): 5
* Max strlen(addr): 12
* Max strlen(dir_port): 4
*/
- char log_match[sizeof(log_template) + 37];
+ char log_match[sizeof(log_with_addrport_tmpl) + 37];
int log_match_len;
- log_match_len = snprintf(log_match, sizeof(log_match), log_template,
- blockers, dir_addr, addr, dir_port);
+ if (addr == NULL)
+ log_match_len = snprintf(log_match, sizeof(log_match),
+ log_without_addrport_tmpl, blockers);
+ else
+ log_match_len = snprintf(log_match, sizeof(log_match),
+ log_with_addrport_tmpl, blockers,
+ dir_addr, addr, dir_port);
if (log_match_len > sizeof(log_match))
return -E2BIG;
@@ -1924,6 +2182,7 @@ static int matches_log_tcp(const int audit_fd, const char *const blockers,
FIXTURE(audit)
{
struct service_fixture srv0;
+ struct service_fixture srv1;
struct audit_filter audit_filter;
int audit_fd;
};
@@ -1935,7 +2194,7 @@ FIXTURE_VARIANT(audit)
};
/* clang-format off */
-FIXTURE_VARIANT_ADD(audit, ipv4) {
+FIXTURE_VARIANT_ADD(audit, ipv4_tcp) {
/* clang-format on */
.addr = "127\\.0\\.0\\.1",
.prot = {
@@ -1945,7 +2204,17 @@ FIXTURE_VARIANT_ADD(audit, ipv4) {
};
/* clang-format off */
-FIXTURE_VARIANT_ADD(audit, ipv6) {
+FIXTURE_VARIANT_ADD(audit, ipv4_udp) {
+ /* clang-format on */
+ .addr = "127\\.0\\.0\\.1",
+ .prot = {
+ .domain = AF_INET,
+ .type = SOCK_DGRAM,
+ },
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(audit, ipv6_tcp) {
/* clang-format on */
.addr = "::1",
.prot = {
@@ -1954,9 +2223,21 @@ FIXTURE_VARIANT_ADD(audit, ipv6) {
},
};
+/* clang-format off */
+FIXTURE_VARIANT_ADD(audit, ipv6_udp) {
+ /* clang-format on */
+ .addr = "::1",
+ .prot = {
+ .domain = AF_INET6,
+ .type = SOCK_DGRAM,
+ },
+};
+
FIXTURE_SETUP(audit)
{
ASSERT_EQ(0, set_service(&self->srv0, variant->prot, 0));
+ ASSERT_EQ(0, set_service(&self->srv1, variant->prot, 1));
+
setup_loopback(_metadata);
set_cap(_metadata, CAP_AUDIT_CONTROL);
@@ -1974,9 +2255,17 @@ FIXTURE_TEARDOWN(audit)
TEST_F(audit, bind)
{
+ const char *audit_evt = (variant->prot.type == SOCK_STREAM ?
+ "net\\.bind_tcp" :
+ "net\\.bind_udp");
+ const int access_rights =
+ (variant->prot.type == SOCK_STREAM ?
+ LANDLOCK_ACCESS_NET_BIND_TCP |
+ LANDLOCK_ACCESS_NET_CONNECT_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .handled_access_net = access_rights,
};
struct audit_records records;
int ruleset_fd, sock_fd;
@@ -1990,8 +2279,8 @@ TEST_F(audit, bind)
sock_fd = socket_variant(&self->srv0);
ASSERT_LE(0, sock_fd);
EXPECT_EQ(-EACCES, bind_variant(sock_fd, &self->srv0));
- EXPECT_EQ(0, matches_log_tcp(self->audit_fd, "net\\.bind_tcp", "saddr",
- variant->addr, "src"));
+ EXPECT_EQ(0, matches_auditlog(self->audit_fd, audit_evt, "saddr",
+ variant->addr, "src"));
EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
EXPECT_EQ(0, records.access);
@@ -2002,9 +2291,22 @@ TEST_F(audit, bind)
TEST_F(audit, connect)
{
+ const char *audit_evt = (variant->prot.type == SOCK_STREAM ?
+ "net\\.connect_tcp" :
+ "net\\.connect_send_udp");
+ const int bind_right = (variant->prot.type == SOCK_STREAM ?
+ LANDLOCK_ACCESS_NET_BIND_TCP :
+ LANDLOCK_ACCESS_NET_BIND_UDP);
+ const int conn_right = (variant->prot.type == SOCK_STREAM ?
+ LANDLOCK_ACCESS_NET_CONNECT_TCP :
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
+ const int access_rights = bind_right | conn_right;
const struct landlock_ruleset_attr ruleset_attr = {
- .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .handled_access_net = access_rights,
+ };
+ const struct landlock_net_port_attr rule_connect_p1 = {
+ .allowed_access = conn_right,
+ .port = self->srv1.port,
};
struct audit_records records;
int ruleset_fd, sock_fd;
@@ -2012,19 +2314,31 @@ TEST_F(audit, connect)
ruleset_fd =
landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
ASSERT_LE(0, ruleset_fd);
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
+ &rule_connect_p1, 0));
enforce_ruleset(_metadata, ruleset_fd);
EXPECT_EQ(0, close(ruleset_fd));
sock_fd = socket_variant(&self->srv0);
ASSERT_LE(0, sock_fd);
EXPECT_EQ(-EACCES, connect_variant(sock_fd, &self->srv0));
- EXPECT_EQ(0, matches_log_tcp(self->audit_fd, "net\\.connect_tcp",
- "daddr", variant->addr, "dest"));
+ EXPECT_EQ(0, matches_auditlog(self->audit_fd, audit_evt, "daddr",
+ variant->addr, "dest"));
EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
EXPECT_EQ(0, records.access);
EXPECT_EQ(1, records.domain);
+ if (variant->prot.type == SOCK_DGRAM) {
+ /* Check that autobind generates a denied bind event. */
+ EXPECT_EQ(-EACCES, connect_variant(sock_fd, &self->srv1));
+
+ EXPECT_EQ(0, matches_auditlog(self->audit_fd, "net\\.bind_udp",
+ NULL, NULL, NULL));
+ EXPECT_EQ(0, records.access);
+ EXPECT_EQ(1, records.domain);
+ }
+
EXPECT_EQ(0, close(sock_fd));
}
--
2.39.5
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v4 5/7] selftests/landlock: Add tests for sendmsg()
2026-05-02 12:42 [PATCH v4 0/7] landlock: Add UDP access control support Matthieu Buffet
` (3 preceding siblings ...)
2026-05-02 12:43 ` [PATCH v4 4/7] selftests/landlock: Add UDP bind/connect tests Matthieu Buffet
@ 2026-05-02 12:43 ` Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 6/7] samples/landlock: Add sandboxer UDP access control Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 7/7] landlock: Add documentation for UDP support Matthieu Buffet
6 siblings, 0 replies; 8+ messages in thread
From: Matthieu Buffet @ 2026-05-02 12:43 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Günther Noack, linux-security-module, Mikhail Ivanov,
konstantin.meskhidze, Tingmao Wang, netdev, Matthieu Buffet
Add tests specific to UDP sendmsg() in the protocol_* variants to ensure
behaviour is consistent across AF_INET, AF_INET6 and AF_UNIX.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
---
tools/testing/selftests/landlock/net_test.c | 652 +++++++++++++++++++-
1 file changed, 651 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
index 568a6ed7139c..2c72fda3c606 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -289,9 +289,163 @@ static int connect_variant(const int sock_fd,
return connect_variant_addrlen(sock_fd, srv, get_addrlen(srv, false));
}
+static int sendto_variant_addrlen(const int sock_fd,
+ const struct service_fixture *const srv,
+ const socklen_t addrlen, void *buf,
+ size_t len, size_t flags)
+{
+ const struct sockaddr *dst = NULL;
+ ssize_t ret;
+
+ /*
+ * We never want our processes to be killed by SIGPIPE: we check
+ * return codes and errno, so that we have actual error messages.
+ */
+ flags |= MSG_NOSIGNAL;
+
+ if (srv != NULL) {
+ switch (srv->protocol.domain) {
+ case AF_UNSPEC:
+ case AF_INET:
+ dst = (const struct sockaddr *)&srv->ipv4_addr;
+ break;
+
+ case AF_INET6:
+ dst = (const struct sockaddr *)&srv->ipv6_addr;
+ break;
+
+ case AF_UNIX:
+ dst = (const struct sockaddr *)&srv->unix_addr;
+ break;
+
+ default:
+ errno = EAFNOSUPPORT;
+ return -errno;
+ }
+ }
+
+ ret = sendto(sock_fd, buf, len, flags, dst, addrlen);
+ if (ret < 0)
+ return -errno;
+
+ /* errno is not set in cases of partial writes. */
+ if (ret != len)
+ return -EINTR;
+
+ return 0;
+}
+
+static int sendto_variant(const int sock_fd,
+ const struct service_fixture *const srv, void *buf,
+ size_t len, size_t flags)
+{
+ socklen_t addrlen = 0;
+
+ if (srv != NULL)
+ addrlen = get_addrlen(srv, false);
+
+ return sendto_variant_addrlen(sock_fd, srv, addrlen, buf, len, flags);
+}
+
+static int test_sendmsg(struct __test_metadata *const _metadata,
+ const struct protocol_variant *prot, int client_fd,
+ int server_fd, const struct service_fixture *srv,
+ bool bind_denied, bool send_denied)
+{
+ int ret;
+ socklen_t opt_len;
+ int sock_type;
+ int addr_family;
+ struct sockaddr_storage peer_addr = { 0 };
+ bool has_remote_port;
+ bool needs_autobind;
+ char read_buf[1] = { 0 };
+
+ /*
+ * Prepare the test by inspecting the socket type and whether it
+ * has a local/remote address set (all of which determine the
+ * expected outcomes).
+ */
+ opt_len = sizeof(sock_type);
+ ASSERT_EQ(0, getsockopt(client_fd, SOL_SOCKET, SO_TYPE, &sock_type,
+ &opt_len));
+ opt_len = sizeof(addr_family);
+ ASSERT_EQ(0, getsockopt(client_fd, SOL_SOCKET, SO_DOMAIN, &addr_family,
+ &opt_len));
+ opt_len = sizeof(peer_addr);
+ has_remote_port = (getpeername(client_fd, (struct sockaddr *)&peer_addr,
+ &opt_len) == 0);
+ needs_autobind = (addr_family == AF_INET || addr_family == AF_INET6) &&
+ get_binded_port(client_fd, prot) == 0;
+
+ /* First, check error code with truncated explicit address. */
+ if (srv != NULL) {
+ ret = sendto_variant_addrlen(
+ client_fd, srv, get_addrlen(srv, true) - 1, "A", 1, 0);
+ if (sock_type == SOCK_STREAM && !has_remote_port) {
+ EXPECT_EQ(-EPIPE, ret)
+ {
+ return -1;
+ }
+ } else if (bind_denied && needs_autobind) {
+ EXPECT_EQ(-EACCES, ret)
+ {
+ return -1;
+ }
+ } else {
+ EXPECT_EQ(-EINVAL, ret)
+ {
+ return -1;
+ }
+ }
+ }
+
+ /* With or without explicit destination address (srv can be NULL). */
+ ret = sendto_variant(client_fd, srv, "B", 1, 0);
+ if (sock_type == SOCK_STREAM && !has_remote_port) {
+ EXPECT_EQ(-EPIPE, ret)
+ {
+ return -1;
+ }
+ } else if ((send_denied && srv != NULL) ||
+ (bind_denied && needs_autobind)) {
+ ASSERT_EQ(-EACCES, ret)
+ {
+ return -1;
+ }
+ } else if (srv == NULL && !has_remote_port) {
+ if (addr_family == AF_UNIX) {
+ ASSERT_EQ(-ENOTCONN, ret)
+ {
+ return -1;
+ }
+ } else if (sock_type == SOCK_STREAM) {
+ ASSERT_EQ(-EPIPE, ret)
+ {
+ return -1;
+ }
+ } else {
+ ASSERT_EQ(-EDESTADDRREQ, ret)
+ {
+ return -1;
+ }
+ }
+ } else {
+ ASSERT_EQ(0, ret);
+ ASSERT_EQ(1, recv(server_fd, read_buf, 1, 0));
+ ASSERT_EQ(read_buf[0], 'B')
+ {
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
FIXTURE(protocol)
{
- struct service_fixture srv0, srv1, srv2, unspec_any0, unspec_srv0;
+ struct service_fixture srv0, srv1, srv2;
+ struct service_fixture unspec_any0, unspec_srv0, unspec_srv1;
};
FIXTURE_VARIANT(protocol)
@@ -313,6 +467,7 @@ FIXTURE_SETUP(protocol)
ASSERT_EQ(0, set_service(&self->srv2, variant->prot, 2));
ASSERT_EQ(0, set_service(&self->unspec_srv0, prot_unspec, 0));
+ ASSERT_EQ(0, set_service(&self->unspec_srv1, prot_unspec, 1));
ASSERT_EQ(0, set_service(&self->unspec_any0, prot_unspec, 0));
self->unspec_any0.ipv4_addr.sin_addr.s_addr = htonl(INADDR_ANY);
@@ -1119,6 +1274,441 @@ TEST_F(protocol, connect_unspec)
EXPECT_EQ(0, close(bind_fd));
}
+TEST_F(protocol, sendmsg_stream)
+{
+ int srv0_fd, tmp_fd, client_fd, res;
+ char read_buf[1] = { 0 };
+
+ /*
+ * Simple test for stream sockets: just deny all connect()/
+ * send(explicit addr)/bind(), and make sure we don't interfere
+ * with any operation.
+ */
+ if (variant->prot.type != SOCK_STREAM)
+ return;
+
+ if (variant->sandbox == UDP_SANDBOX) {
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_net =
+ LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ };
+ const int ruleset_fd = landlock_create_ruleset(
+ &ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ EXPECT_EQ(0, close(ruleset_fd));
+ }
+
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+ ASSERT_LE(0, srv0_fd = socket_variant(&self->srv0));
+ ASSERT_EQ(0, bind_variant(srv0_fd, &self->srv0));
+ ASSERT_EQ(0, listen(srv0_fd, backlog));
+
+ /* Send on a non-connected socket. */
+ res = sendto_variant(client_fd, NULL, "A", 1, 0);
+ if (variant->prot.domain == AF_UNIX) {
+ EXPECT_EQ(-ENOTCONN, res);
+ } else {
+ EXPECT_EQ(-EPIPE, res);
+ }
+
+ /* Send to a truncated (invalid) address on a non-connected socket. */
+ res = sendto_variant_addrlen(client_fd, &self->srv0,
+ get_addrlen(&self->srv0, true) - 1, "B", 1,
+ 0);
+ if (variant->prot.domain == AF_UNIX) {
+ EXPECT_EQ(-EOPNOTSUPP, res);
+ } else {
+ EXPECT_EQ(-EPIPE, res);
+ }
+
+ /* Connect. */
+ ASSERT_EQ(0, connect_variant(client_fd, &self->srv0));
+ tmp_fd = accept(srv0_fd, NULL, 0);
+ ASSERT_LE(0, tmp_fd);
+ EXPECT_EQ(0, close(srv0_fd));
+ srv0_fd = tmp_fd;
+
+ /* Send without an explicit address. */
+ EXPECT_EQ(0, sendto_variant(client_fd, NULL, "C", 1, 0));
+ EXPECT_EQ(1, recv(srv0_fd, read_buf, 1, 0))
+ {
+ TH_LOG("recv() failed: %s", strerror(errno));
+ }
+ EXPECT_EQ(read_buf[0], 'C');
+
+ /* Send to a truncated (invalid) address. */
+ res = sendto_variant_addrlen(client_fd, &self->srv0,
+ get_addrlen(&self->srv0, true) - 1, "D", 1,
+ 0);
+ if (variant->prot.domain == AF_UNIX) {
+ EXPECT_EQ(-EISCONN, res);
+ } else {
+ EXPECT_EQ(0, res);
+ EXPECT_EQ(1, recv(srv0_fd, read_buf, 1, 0))
+ {
+ TH_LOG("recv() failed: %s", strerror(errno));
+ }
+ EXPECT_EQ(read_buf[0], 'D');
+ }
+
+ /* Send to a valid but different address. */
+ res = sendto_variant(client_fd, &self->srv1, "E", 1, 0);
+ if (variant->prot.domain == AF_UNIX) {
+ EXPECT_EQ(-EISCONN, res);
+ } else {
+ EXPECT_EQ(0, res);
+ EXPECT_EQ(1, recv(srv0_fd, read_buf, 1, 0))
+ {
+ TH_LOG("recv() failed: %s", strerror(errno));
+ }
+ EXPECT_EQ(read_buf[0], 'E');
+ }
+
+ EXPECT_EQ(0, close(client_fd));
+}
+
+TEST_F(protocol, sendmsg_dgram)
+{
+ const bool restricted = is_restricted(&variant->prot, variant->sandbox);
+ int srv0_fd, srv1_fd, client_fd, child, status, res;
+
+ if (variant->prot.type != SOCK_DGRAM)
+ return;
+
+ /* Prepare server on port #0 to be allowed. */
+ ASSERT_LE(0, srv0_fd = socket_variant(&self->srv0));
+ ASSERT_EQ(0, bind_variant(srv0_fd, &self->srv0));
+
+ /* And another server on port #1 to be denied. */
+ ASSERT_LE(0, srv1_fd = socket_variant(&self->srv1));
+ ASSERT_EQ(0, bind_variant(srv1_fd, &self->srv1));
+
+ /*
+ * Check that sockets connected before restrictions are not
+ * impacted in any way.
+ */
+ child = fork();
+ ASSERT_LE(0, child);
+ if (child == 0) {
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+ ASSERT_EQ(0, connect_variant(client_fd, &self->srv0));
+ if (variant->sandbox == UDP_SANDBOX) {
+ /* Deny all connect()/send(explicit addr)/bind(). */
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_net =
+ LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ };
+ const int ruleset_fd = landlock_create_ruleset(
+ &ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ EXPECT_EQ(0, close(ruleset_fd));
+ }
+ EXPECT_EQ(0,
+ test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv0_fd, NULL, restricted, restricted));
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv0_fd, &self->srv0, restricted,
+ restricted));
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv1_fd, &self->srv1, restricted,
+ restricted));
+ EXPECT_EQ(0, close(client_fd));
+ _exit(_metadata->exit_code);
+ }
+ EXPECT_EQ(child, waitpid(child, &status, 0));
+ EXPECT_EQ(1, WIFEXITED(status));
+ EXPECT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
+
+ /*
+ * Restrict connect/send, but not bind(). Then try sending with
+ * no destination (and no remote peer set), an allowed
+ * destination, then a denied destination.
+ */
+ child = fork();
+ ASSERT_LE(0, child);
+ if (child == 0) {
+ if (variant->sandbox == UDP_SANDBOX) {
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_net =
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ };
+ const struct landlock_net_port_attr send_p0 = {
+ .allowed_access =
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ .port = self->srv0.port,
+ };
+ const int ruleset_fd = landlock_create_ruleset(
+ &ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
+ LANDLOCK_RULE_NET_PORT,
+ &send_p0, 0));
+ enforce_ruleset(_metadata, ruleset_fd);
+ EXPECT_EQ(0, close(ruleset_fd));
+ }
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ -1, NULL, false, false));
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv0_fd, &self->srv0, false, false));
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv1_fd, &self->srv1, false,
+ restricted));
+ EXPECT_EQ(0, close(client_fd));
+ _exit(_metadata->exit_code);
+ return;
+ }
+ EXPECT_EQ(child, waitpid(child, &status, 0));
+ EXPECT_EQ(1, WIFEXITED(status));
+ EXPECT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
+
+ /*
+ * Rest of this test is just for autobind enforcement, which only
+ * exists in IP sockets.
+ */
+ if (variant->prot.domain != AF_INET && variant->prot.domain != AF_INET6)
+ return;
+
+ /* Restrict bind() to explicit calls with an arbitrary (non-0) port. */
+ child = fork();
+ ASSERT_LE(0, child);
+ if (child == 0) {
+ const uint16_t allowed_src_port = 42424;
+ struct service_fixture allowed_src;
+
+ allowed_src = self->srv0;
+ set_port(&allowed_src, allowed_src_port);
+ if (variant->sandbox == UDP_SANDBOX) {
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_net =
+ LANDLOCK_ACCESS_NET_BIND_UDP,
+ };
+ const struct landlock_net_port_attr rule = {
+ .allowed_access = LANDLOCK_ACCESS_NET_BIND_UDP,
+ .port = allowed_src_port,
+ };
+ const int ruleset_fd = landlock_create_ruleset(
+ &ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
+ LANDLOCK_RULE_NET_PORT,
+ &rule, 0));
+ enforce_ruleset(_metadata, ruleset_fd);
+ EXPECT_EQ(0, close(ruleset_fd));
+ }
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+
+ /* Check that implicit bind(0) in sendmsg() is denied. */
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv0_fd, &self->srv0, restricted,
+ false));
+
+ /* Same thing for autobind in connect(). */
+ res = connect_variant(client_fd, &self->srv0);
+ if (restricted) {
+ EXPECT_EQ(-EACCES, res);
+ } else {
+ EXPECT_EQ(0, res);
+ }
+ EXPECT_EQ(0, close(client_fd));
+
+ /* Make sendmsg() work by explicitly binding to the only allowed port. */
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+ EXPECT_EQ(0, bind_variant(client_fd, &allowed_src));
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv0_fd, &self->srv0, restricted,
+ false));
+ EXPECT_EQ(0, close(client_fd));
+
+ /* Make connect() work by explicitly binding to the only allowed port. */
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+ EXPECT_EQ(0, bind_variant(client_fd, &allowed_src));
+ EXPECT_EQ(0, connect_variant(client_fd, &self->srv0));
+ EXPECT_EQ(0, close(client_fd));
+
+ _exit(_metadata->exit_code);
+ return;
+ }
+ EXPECT_EQ(child, waitpid(child, &status, 0));
+ EXPECT_EQ(1, WIFEXITED(status));
+ EXPECT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
+
+ /*
+ * Check that %LANDLOCK_ACCESS_NET_BIND_UDP on port 0 allows
+ * implicit autobinds.
+ */
+ child = fork();
+ ASSERT_LE(0, child);
+ if (child == 0) {
+ if (variant->sandbox == UDP_SANDBOX) {
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_net =
+ LANDLOCK_ACCESS_NET_BIND_UDP,
+ };
+ const struct landlock_net_port_attr rule = {
+ .allowed_access = LANDLOCK_ACCESS_NET_BIND_UDP,
+ .port = 0,
+ };
+ const int ruleset_fd = landlock_create_ruleset(
+ &ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
+ LANDLOCK_RULE_NET_PORT,
+ &rule, 0));
+ enforce_ruleset(_metadata, ruleset_fd);
+ EXPECT_EQ(0, close(ruleset_fd));
+ }
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+ EXPECT_EQ(0, test_sendmsg(_metadata, &variant->prot, client_fd,
+ srv0_fd, &self->srv0, false, false));
+ EXPECT_EQ(0, close(client_fd));
+ _exit(_metadata->exit_code);
+ }
+ EXPECT_EQ(child, waitpid(child, &status, 0));
+ EXPECT_EQ(1, WIFEXITED(status));
+ EXPECT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
+}
+
+TEST_F(protocol, sendmsg_unspec)
+{
+ const bool restricted = is_restricted(&variant->prot, variant->sandbox);
+ int client_fd, srv0_fd, srv1_fd, res;
+ char read_buf[1] = { 0 };
+
+ /*
+ * We already test for the absence of influence on sendmsg for
+ * other socket types and other address families, there's no
+ * point in adapting this test for stream sockets too.
+ */
+ if (variant->prot.type != SOCK_DGRAM)
+ return;
+
+ /* Prepare client of the right family. */
+ ASSERT_LE(0, client_fd = socket_variant(&self->srv0));
+
+ /* Prepare server on port #0 to be allowed. */
+ ASSERT_LE(0, srv0_fd = socket_variant(&self->srv0));
+ ASSERT_EQ(0, bind_variant(srv0_fd, &self->srv0));
+
+ /* And another server on port #1 to be denied. */
+ ASSERT_LE(0, srv1_fd = socket_variant(&self->srv1));
+ ASSERT_EQ(0, bind_variant(srv1_fd, &self->srv1));
+
+ if (variant->sandbox == UDP_SANDBOX) {
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_net =
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ };
+ const struct landlock_net_port_attr rule = {
+ .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ .port = self->srv0.port,
+ };
+ const int ruleset_fd = landlock_create_ruleset(
+ &ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ ASSERT_EQ(0,
+ landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
+ &rule, 0));
+ enforce_ruleset(_metadata, ruleset_fd);
+ EXPECT_EQ(0, close(ruleset_fd));
+ }
+
+ /* Explicit AF_UNSPEC address but truncated. */
+ EXPECT_EQ(-EINVAL, sendto_variant_addrlen(
+ client_fd, &self->unspec_srv0,
+ get_addrlen(&self->unspec_srv0, true) - 1,
+ "A", 1, 0));
+
+ /*
+ * Explicit AF_UNSPEC address, should be treated as AF_INET by
+ * IPv4 sockets (and thus map to srv0, allowed), but be denied by
+ * IPv6 sockets.
+ */
+ res = sendto_variant(client_fd, &self->unspec_srv0, "B", 1, 0);
+ if (variant->prot.domain == AF_INET6) {
+ if (restricted) {
+ /* Always denied on IPv6 socket. */
+ EXPECT_EQ(-EACCES, res);
+ } else {
+ /* IPv6 sockets treat AF_UNSPEC as a NULL address. */
+ EXPECT_EQ(-EDESTADDRREQ, res);
+ }
+ } else if (variant->prot.domain == AF_INET) {
+ EXPECT_EQ(0, res);
+ EXPECT_EQ(1, read(srv0_fd, read_buf, 1))
+ {
+ TH_LOG("read() failed: %s", strerror(errno));
+ }
+ EXPECT_EQ(read_buf[0], 'B');
+ } else {
+ /* Unix sockets don't accept AF_UNSPEC. */
+ EXPECT_EQ(-EINVAL, res);
+ }
+
+ /*
+ * Explicit AF_UNSPEC address, should be treated as AF_INET on
+ * IPv4 sockets (and thus map to srv1, denied), and be denied
+ * on IPv6 sockets as always.
+ */
+ res = sendto_variant(client_fd, &self->unspec_srv1, "C", 1, 0);
+ if (variant->prot.domain == AF_INET6) {
+ if (restricted) {
+ /* Always denied on IPv6 socket. */
+ EXPECT_EQ(-EACCES, res);
+ } else {
+ /* IPv6 sockets treat AF_UNSPEC as a NULL address. */
+ EXPECT_EQ(-EDESTADDRREQ, res);
+ }
+ } else if (variant->prot.domain == AF_INET) {
+ if (restricted) {
+ /* Sending to srv1 is not allowed, only srv0. */
+ EXPECT_EQ(-EACCES, res);
+ } else {
+ EXPECT_EQ(0, res);
+ EXPECT_EQ(1, read(srv1_fd, read_buf, 1))
+ {
+ TH_LOG("read() failed: %s", strerror(errno));
+ }
+ EXPECT_EQ(read_buf[0], 'C');
+ }
+ } else {
+ /* Unix sockets don't accept AF_UNSPEC. */
+ EXPECT_EQ(-EINVAL, res);
+ }
+
+ ASSERT_EQ(0, connect_variant(client_fd, &self->srv0));
+
+ /* Minimal explicit AF_UNSPEC address (just the sa_family_t field) */
+ res = sendto_variant_addrlen(client_fd, &self->unspec_srv0,
+ get_addrlen(&self->unspec_srv0, true), "D",
+ 1, 0);
+ if (variant->prot.domain == AF_INET6) {
+ if (restricted) {
+ /* AF_UNSPEC is always denied in IPv6. */
+ EXPECT_EQ(-EACCES, res);
+ } else {
+ /*
+ * IPv6 sockets treat AF_UNSPEC as a NULL address,
+ * falling back to the connected address.
+ */
+ EXPECT_EQ(0, res);
+ EXPECT_EQ(1, read(srv0_fd, read_buf, 1));
+ EXPECT_EQ(read_buf[0], 'D');
+ }
+ } else {
+ /*
+ * IPv4 socket will expect a struct sockaddr_in, our address
+ * is considered truncated.
+ * And Unix sockets don't accept AF_UNSPEC at all.
+ */
+ EXPECT_EQ(-EINVAL, res);
+ }
+}
+
FIXTURE(ipv4)
{
struct service_fixture srv0, srv1;
@@ -2183,6 +2773,7 @@ FIXTURE(audit)
{
struct service_fixture srv0;
struct service_fixture srv1;
+ struct service_fixture unspec_srv0;
struct audit_filter audit_filter;
int audit_fd;
};
@@ -2235,8 +2826,13 @@ FIXTURE_VARIANT_ADD(audit, ipv6_udp) {
FIXTURE_SETUP(audit)
{
+ struct protocol_variant prot_unspec = variant->prot;
+
+ prot_unspec.domain = AF_UNSPEC;
+
ASSERT_EQ(0, set_service(&self->srv0, variant->prot, 0));
ASSERT_EQ(0, set_service(&self->srv1, variant->prot, 1));
+ ASSERT_EQ(0, set_service(&self->unspec_srv0, prot_unspec, 0));
setup_loopback(_metadata);
@@ -2342,4 +2938,58 @@ TEST_F(audit, connect)
EXPECT_EQ(0, close(sock_fd));
}
+TEST_F(audit, sendmsg)
+{
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_net = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP |
+ LANDLOCK_ACCESS_NET_BIND_UDP,
+ };
+ const struct landlock_net_port_attr rule = {
+ .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ .port = self->srv1.port,
+ };
+ const int ruleset_fd =
+ landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+ struct audit_records records;
+ int sock_fd;
+
+ /* Sendmsg on stream sockets is never denied. */
+ if (variant->prot.type != SOCK_DGRAM)
+ return;
+
+ ASSERT_LE(0, ruleset_fd);
+ ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
+ &rule, 0));
+ enforce_ruleset(_metadata, ruleset_fd);
+ EXPECT_EQ(0, close(ruleset_fd));
+
+ sock_fd = socket_variant(&self->srv0);
+ ASSERT_LE(0, sock_fd);
+ EXPECT_EQ(-EACCES, sendto_variant(sock_fd, &self->srv0, "A", 1, 0));
+ EXPECT_EQ(0, matches_auditlog(self->audit_fd, "net\\.connect_send_udp",
+ "daddr", variant->addr, "dest"));
+
+ EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
+ EXPECT_EQ(0, records.access);
+ EXPECT_EQ(1, records.domain);
+
+ /* Check that autobind generates a denied bind event. */
+ EXPECT_EQ(-EACCES, sendto_variant(sock_fd, &self->srv1, "A", 1, 0));
+ EXPECT_EQ(0, matches_auditlog(self->audit_fd, "net\\.bind_udp", NULL,
+ NULL, NULL));
+ EXPECT_EQ(0, records.access);
+ EXPECT_EQ(1, records.domain);
+
+ EXPECT_EQ(-EACCES,
+ sendto_variant(sock_fd, &self->unspec_srv0, "B", 1, 0));
+ EXPECT_EQ(0, matches_auditlog(self->audit_fd, "net\\.connect_send_udp",
+ "daddr", NULL, "dest"));
+
+ EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
+ EXPECT_EQ(0, records.access);
+ EXPECT_EQ(0, records.domain);
+
+ EXPECT_EQ(0, close(sock_fd));
+}
+
TEST_HARNESS_MAIN
--
2.39.5
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v4 6/7] samples/landlock: Add sandboxer UDP access control
2026-05-02 12:42 [PATCH v4 0/7] landlock: Add UDP access control support Matthieu Buffet
` (4 preceding siblings ...)
2026-05-02 12:43 ` [PATCH v4 5/7] selftests/landlock: Add tests for sendmsg() Matthieu Buffet
@ 2026-05-02 12:43 ` Matthieu Buffet
2026-05-02 12:43 ` [PATCH v4 7/7] landlock: Add documentation for UDP support Matthieu Buffet
6 siblings, 0 replies; 8+ messages in thread
From: Matthieu Buffet @ 2026-05-02 12:43 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Günther Noack, linux-security-module, Mikhail Ivanov,
konstantin.meskhidze, Tingmao Wang, netdev, Matthieu Buffet
Add environment variables to control associated access rights:
- LL_UDP_BIND
- LL_UDP_CONNECT_SEND
Each one takes a list of ports separated by colons, like other list
options.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
---
samples/landlock/sandboxer.c | 40 ++++++++++++++++++++++++++++++++++--
1 file changed, 38 insertions(+), 2 deletions(-)
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 66e56ae275c6..94e399e6b146 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -62,6 +62,8 @@ static inline int landlock_restrict_self(const int ruleset_fd,
#define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"
#define ENV_SCOPED_NAME "LL_SCOPED"
#define ENV_FORCE_LOG_NAME "LL_FORCE_LOG"
+#define ENV_UDP_BIND_NAME "LL_UDP_BIND"
+#define ENV_UDP_CONNECT_SEND_NAME "LL_UDP_CONNECT_SEND"
#define ENV_DELIMITER ":"
static int str2num(const char *numstr, __u64 *num_dst)
@@ -301,7 +303,7 @@ static bool check_ruleset_scope(const char *const env_var,
/* clang-format on */
-#define LANDLOCK_ABI_LAST 9
+#define LANDLOCK_ABI_LAST 10
#define XSTR(s) #s
#define STR(s) XSTR(s)
@@ -324,6 +326,10 @@ static const char help[] =
"means an empty list):\n"
"* " ENV_TCP_BIND_NAME ": ports allowed to bind (server)\n"
"* " ENV_TCP_CONNECT_NAME ": ports allowed to connect (client)\n"
+ "* " ENV_UDP_BIND_NAME ": local UDP ports allowed to bind (server: "
+ "prepare to receive on port / client: set as source port)\n"
+ "* " ENV_UDP_CONNECT_SEND_NAME ": remote UDP ports allowed to connect "
+ "or sendmsg (client: use as destination port / server: receive only from it)\n"
"* " ENV_SCOPED_NAME ": actions denied on the outside of the landlock domain\n"
" - \"a\" to restrict opening abstract unix sockets\n"
" - \"s\" to restrict sending signals\n"
@@ -336,6 +342,7 @@ static const char help[] =
ENV_FS_RW_NAME "=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
ENV_TCP_BIND_NAME "=\"9418\" "
ENV_TCP_CONNECT_NAME "=\"80:443\" "
+ ENV_UDP_CONNECT_SEND_NAME "=\"53\" "
ENV_SCOPED_NAME "=\"a:s\" "
"%1$s bash -i\n"
"\n"
@@ -356,7 +363,9 @@ int main(const int argc, char *const argv[], char *const *const envp)
struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = access_fs_rw,
.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ LANDLOCK_ACCESS_NET_CONNECT_TCP |
+ LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
.scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |
LANDLOCK_SCOPE_SIGNAL,
};
@@ -444,6 +453,13 @@ int main(const int argc, char *const argv[], char *const *const envp)
/* Removes LANDLOCK_ACCESS_FS_RESOLVE_UNIX for ABI < 9 */
ruleset_attr.handled_access_fs &=
~LANDLOCK_ACCESS_FS_RESOLVE_UNIX;
+ __attribute__((fallthrough));
+ case 9:
+ /* Removes UDP support for ABI < 10 */
+ ruleset_attr.handled_access_net &=
+ ~(LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
+
/* Must be printed for any ABI < LANDLOCK_ABI_LAST. */
fprintf(stderr,
"Hint: You should update the running kernel "
@@ -475,6 +491,18 @@ int main(const int argc, char *const argv[], char *const *const envp)
ruleset_attr.handled_access_net &=
~LANDLOCK_ACCESS_NET_CONNECT_TCP;
}
+ /* Removes UDP bind access control if not supported by a user. */
+ env_port_name = getenv(ENV_UDP_BIND_NAME);
+ if (!env_port_name) {
+ ruleset_attr.handled_access_net &=
+ ~LANDLOCK_ACCESS_NET_BIND_UDP;
+ }
+ /* Removes UDP connect/send access control if not supported by a user. */
+ env_port_name = getenv(ENV_UDP_CONNECT_SEND_NAME);
+ if (!env_port_name) {
+ ruleset_attr.handled_access_net &=
+ ~LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP;
+ }
if (check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr))
return 1;
@@ -519,6 +547,14 @@ int main(const int argc, char *const argv[], char *const *const envp)
LANDLOCK_ACCESS_NET_CONNECT_TCP)) {
goto err_close_ruleset;
}
+ if (populate_ruleset_net(ENV_UDP_BIND_NAME, ruleset_fd,
+ LANDLOCK_ACCESS_NET_BIND_UDP)) {
+ goto err_close_ruleset;
+ }
+ if (populate_ruleset_net(ENV_UDP_CONNECT_SEND_NAME, ruleset_fd,
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP)) {
+ goto err_close_ruleset;
+ }
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
perror("Failed to restrict privileges");
--
2.39.5
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v4 7/7] landlock: Add documentation for UDP support
2026-05-02 12:42 [PATCH v4 0/7] landlock: Add UDP access control support Matthieu Buffet
` (5 preceding siblings ...)
2026-05-02 12:43 ` [PATCH v4 6/7] samples/landlock: Add sandboxer UDP access control Matthieu Buffet
@ 2026-05-02 12:43 ` Matthieu Buffet
6 siblings, 0 replies; 8+ messages in thread
From: Matthieu Buffet @ 2026-05-02 12:43 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Günther Noack, linux-security-module, Mikhail Ivanov,
konstantin.meskhidze, Tingmao Wang, netdev, Matthieu Buffet
Add example of UDP usage, without detailing the two access right.
Slightly change the example used in code blocks: build a ruleset for a
DNS client, so that it uses both TCP and UDP.
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
---
Documentation/userspace-api/landlock.rst | 89 ++++++++++++++++++------
1 file changed, 68 insertions(+), 21 deletions(-)
diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index fd8b78c31f2f..9d5da9896628 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst
@@ -40,8 +40,8 @@ Filesystem rules
and the related filesystem actions are defined with
`filesystem access rights`.
-Network rules (since ABI v4)
- For these rules, the object is a TCP port,
+Network rules (since ABI v4 for TCP and v10 for UDP)
+ For these rules, the object is a TCP or UDP port,
and the related actions are defined with `network access rights`.
Defining and enforcing a security policy
@@ -49,11 +49,11 @@ Defining and enforcing a security policy
We first need to define the ruleset that will contain our rules.
-For this example, the ruleset will contain rules that only allow filesystem
-read actions and establish a specific TCP connection. Filesystem write
-actions and other TCP actions will be denied.
+For this example, the ruleset will contain rules that only allow some
+filesystem read actions and some specific UDP and TCP actions. Filesystem
+write actions and other TCP/UDP actions will be denied.
-The ruleset then needs to handle both these kinds of actions. This is
+The ruleset then needs to handle all these kinds of actions. This is
required for backward and forward compatibility (i.e. the kernel and user
space may not know each other's supported restrictions), hence the need
to be explicit about the denied-by-default access rights.
@@ -81,7 +81,9 @@ to be explicit about the denied-by-default access rights.
LANDLOCK_ACCESS_FS_RESOLVE_UNIX,
.handled_access_net =
LANDLOCK_ACCESS_NET_BIND_TCP |
- LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ LANDLOCK_ACCESS_NET_CONNECT_TCP |
+ LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
.scoped =
LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |
LANDLOCK_SCOPE_SIGNAL,
@@ -132,6 +134,12 @@ version, and only use the available subset of access rights:
case 6 ... 8:
/* Removes LANDLOCK_ACCESS_FS_RESOLVE_UNIX for ABI < 9 */
ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_RESOLVE_UNIX;
+ __attribute__((fallthrough));
+ case 9:
+ /* Removes LANDLOCK_ACCESS_*_UDP for ABI < 10 */
+ ruleset_attr.handled_access_net &=
+ ~(LANDLOCK_ACCESS_NET_BIND_UDP |
+ LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP);
}
This enables the creation of an inclusive ruleset that will contain our rules.
@@ -180,21 +188,50 @@ this file descriptor.
It may also be required to create rules following the same logic as explained
for the ruleset creation, by filtering access rights according to the Landlock
-ABI version. In this example, this is not required because all of the requested
-``allowed_access`` rights are already available in ABI 1.
+ABI version. So far, this was not required because all of the requested
+``allowed_access`` rights have always been available, from ABI 1.
-For network access-control, we can add a set of rules that allow to use a port
-number for a specific action: HTTPS connections.
+For network access-control, we will add a set of rules to allow DNS
+queries, which requires both UDP and TCP. For TCP, we need to allow
+outbound connections to port 53, which can be handled and granted starting
+with ABI 4:
.. code-block:: c
- struct landlock_net_port_attr net_port = {
- .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
- .port = 443,
- };
+ if (ruleset_attr.handled_access_net & LANDLOCK_ACCESS_NET_CONNECT_TCP) {
+ struct landlock_net_port_attr net_port = {
+ .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .port = 53,
+ };
- err = landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
- &net_port, 0);
+ err = landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
+ &net_port, 0);
+
+We also need to be able to send UDP datagrams to port 53, which requires
+granting ``LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP``. Since our DNS client will
+emit datagrams without explicitly binding to a specific source port, its UDP
+socket will automatically bind an ephemeral port. To allow this behaviour,
+we also need to grant ``LANDLOCK_ACCESS_NET_BIND_UDP`` on port 0, as if
+the program explicitly called :manpage:`bind(2)` on port 0.
+
+.. code-block:: c
+
+ if (ruleset_attr.handled_access_net & LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) {
+ const struct landlock_net_port_attr send_dst_port = {
+ .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP,
+ .port = 53,
+ };
+ err = landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
+ &send_dst_port, 0);
+ [...]
+
+ if (ruleset_attr.handled_access_net & LANDLOCK_ACCESS_NET_BIND_UDP) {
+ const struct landlock_net_port_attr bind_src_port = {
+ .allowed_access = LANDLOCK_ACCESS_NET_BIND_UDP,
+ .port = 0,
+ };
+ err = landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
+ &bind_src_port, 0);
When passing a non-zero ``flags`` argument to ``landlock_restrict_self()``, a
similar backwards compatibility check is needed for the restrict flags
@@ -228,7 +265,7 @@ similar backwards compatibility check is needed for the restrict flags
The next step is to restrict the current thread from gaining more privileges
(e.g. through a SUID binary). We now have a ruleset with the first rule
allowing read and execute access to ``/usr`` while denying all other handled
-accesses for the filesystem, and a second rule allowing HTTPS connections.
+accesses for the filesystem, and two more rules allowing DNS queries.
.. code-block:: c
@@ -716,6 +753,16 @@ Starting with the Landlock ABI version 9, it is possible to restrict
connections to pathname UNIX domain sockets (:manpage:`unix(7)`) using
the new ``LANDLOCK_ACCESS_FS_RESOLVE_UNIX`` right.
+UDP bind, connect, sendto, sendmsg and sendmmsg (ABI < 10)
+----------------------------------------------------------
+
+Starting with the Landlock ABI version 10, it is possible to restrict
+setting the local port of UDP sockets with the
+``LANDLOCK_ACCESS_NET_BIND_UDP`` right.
+The ``LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP`` right controls setting the
+remote port of UDP sockets, and sending datagrams to an explicit remote
+port (ignoring any destination set on UDP sockets).
+
.. _kernel_support:
Kernel support
@@ -778,10 +825,10 @@ the boot loader.
Network support
---------------
-To be able to explicitly allow TCP operations (e.g., adding a network rule with
-``LANDLOCK_ACCESS_NET_BIND_TCP``), the kernel must support TCP
+To be able to explicitly allow TCP or UDP operations (e.g., adding a network rule with
+``LANDLOCK_ACCESS_NET_BIND_TCP``), the kernel must support the TCP/IP protocol suite
(``CONFIG_INET=y``). Otherwise, sys_landlock_add_rule() returns an
-``EAFNOSUPPORT`` error, which can safely be ignored because this kind of TCP
+``EAFNOSUPPORT`` error, which can safely be ignored because this kind of TCP or UDP
operation is already not possible.
Questions and answers
--
2.39.5
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