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Message-ID: <20250613222411.1216170-4-kuni1840@gmail.com>
Date: Fri, 13 Jun 2025 15:22:15 -0700
From: Kuniyuki Iwashima <kuni1840@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii@...nel.org>
Cc: Eduard Zingerman <eddyz87@...il.com>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...ichev.me>,
Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
Kumar Kartikeya Dwivedi <memxor@...il.com>,
Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Mickaël Salaün <mic@...ikod.net>,
Günther Noack <gnoack@...gle.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Ondrej Mosnacek <omosnace@...hat.com>,
Casey Schaufler <casey@...aufler-ca.com>,
Kuniyuki Iwashima <kuniyu@...gle.com>,
Kuniyuki Iwashima <kuni1840@...il.com>,
bpf@...r.kernel.org,
linux-security-module@...r.kernel.org,
selinux@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH v2 bpf-next 3/4] af_unix: Pass skb to security_unix_may_send().
From: Kuniyuki Iwashima <kuniyu@...gle.com>
SO_PASSRIGHTS is not flexible as it cannot control what types
of file descriptors are allowed to be passed.
Let's pass skb to security_unix_may_send() so that we can
implement more fine-grained filtering logic with BPF LSM.
Note that only the LSM_HOOK() macro uses the __nullable suffix
for skb to inform the verifier that the skb could be NULL at
connect(). Without it, I was able to load a bpf prog without
NULL check against skb.
Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
include/linux/lsm_hook_defs.h | 3 ++-
include/linux/security.h | 5 +++--
net/unix/af_unix.c | 8 ++++----
security/landlock/task.c | 3 ++-
security/security.c | 5 +++--
security/selinux/hooks.c | 3 ++-
security/smack/smack_lsm.c | 3 ++-
7 files changed, 18 insertions(+), 12 deletions(-)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 9be001922e0b..80edfe85214e 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -318,7 +318,8 @@ LSM_HOOK(int, 0, watch_key, struct key *key)
#ifdef CONFIG_SECURITY_NETWORK
LSM_HOOK(int, 0, unix_stream_connect, struct sock *sock, struct sock *other,
struct sock *newsk)
-LSM_HOOK(int, 0, unix_may_send, struct sock *sock, struct sock *other)
+LSM_HOOK(int, 0, unix_may_send, struct sock *sock, struct sock *other,
+ struct sk_buff *skb__nullable)
LSM_HOOK(int, 0, socket_create, int family, int type, int protocol, int kern)
LSM_HOOK(int, 0, socket_post_create, struct socket *sock, int family, int type,
int protocol, int kern)
diff --git a/include/linux/security.h b/include/linux/security.h
index 36aa7030e16d..922618a98f15 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1625,7 +1625,7 @@ static inline int security_watch_key(struct key *key)
int security_netlink_send(struct sock *sk, struct sk_buff *skb);
int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk);
-int security_unix_may_send(struct sock *sk, struct sock *other);
+int security_unix_may_send(struct sock *sk, struct sock *other, struct sk_buff *skb);
int security_socket_create(int family, int type, int protocol, int kern);
int security_socket_post_create(struct socket *sock, int family,
int type, int protocol, int kern);
@@ -1692,7 +1692,8 @@ static inline int security_unix_stream_connect(struct sock *sock,
}
static inline int security_unix_may_send(struct sock *sk,
- struct sock *other)
+ struct sock *other,
+ struct sk_buff *skb)
{
return 0;
}
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index bcbe0c86e001..fd6b5e17f6c4 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1516,7 +1516,7 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
if (!unix_may_send(sk, other))
goto out_unlock;
- err = security_unix_may_send(sk, other);
+ err = security_unix_may_send(sk, other, NULL);
if (err)
goto out_unlock;
@@ -2170,7 +2170,7 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
goto out_unlock;
}
- err = security_unix_may_send(sk, other);
+ err = security_unix_may_send(sk, other, skb);
if (err)
goto out_unlock;
@@ -2279,7 +2279,7 @@ static int queue_oob(struct sock *sk, struct msghdr *msg, struct sock *other,
}
if (!fds_sent) {
- err = security_unix_may_send(sk, other);
+ err = security_unix_may_send(sk, other, skb);
if (err)
goto out_unlock;
}
@@ -2406,7 +2406,7 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
}
if (!fds_sent) {
- err = security_unix_may_send(sk, other);
+ err = security_unix_may_send(sk, other, skb);
if (err)
goto out_unlock;
diff --git a/security/landlock/task.c b/security/landlock/task.c
index 6bc6f3027790..f243edb036a7 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -295,7 +295,8 @@ static int hook_unix_stream_connect(struct sock *const sock,
}
static int hook_unix_may_send(struct sock *const sk,
- struct sock *const other)
+ struct sock *const other,
+ struct sk_buff *skb)
{
size_t handle_layer;
const struct landlock_cred_security *const subject =
diff --git a/security/security.c b/security/security.c
index 3bd8eec01d05..3362e5b6764f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -4531,9 +4531,10 @@ EXPORT_SYMBOL(security_unix_stream_connect);
*
* Return: Returns 0 if permission is granted.
*/
-int security_unix_may_send(struct sock *sk, struct sock *other)
+int security_unix_may_send(struct sock *sk, struct sock *other,
+ struct sk_buff *skb)
{
- return call_int_hook(unix_may_send, sk, other);
+ return call_int_hook(unix_may_send, sk, other, skb);
}
EXPORT_SYMBOL(security_unix_may_send);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 904926ef9ee8..dec0abbc60d5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5177,7 +5177,8 @@ static int selinux_socket_unix_stream_connect(struct sock *sock,
}
static int selinux_socket_unix_may_send(struct sock *sk,
- struct sock *other)
+ struct sock *other,
+ struct sk_buff *skb)
{
struct sk_security_struct *ssec = selinux_sock(sk);
struct sk_security_struct *osec = selinux_sock(other);
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 20fe1d22210e..2fd2c1be5bbb 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3889,7 +3889,8 @@ static int smack_unix_stream_connect(struct sock *sock,
* Return 0 if a subject with the smack of sock could access
* an object with the smack of other, otherwise an error code
*/
-static int smack_unix_may_send(struct sock *sk, struct sock *other)
+static int smack_unix_may_send(struct sock *sk, struct sock *other,
+ struct sk_buff *skb)
{
struct socket_smack *ssp = smack_sock(sk);
struct socket_smack *osp = smack_sock(other);
--
2.49.0
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