[PATCH v7 bpf-next 11/18] bpf, lsm: add bpf_token_create and bpf_token_free LSM hooks

[Andrii Nakryiko]

Wire up bpf_token_create and bpf_token_free LSM hooks, which allow to
allocate LSM security blob (we add `void *security` field to struct
bpf_token for that), but also control who can instantiate BPF token.
This follows existing pattern for BPF map and BPF prog.

Signed-off-by: Andrii Nakryiko <andrii at kernel.org>
---
 include/linux/bpf.h           |  3 +++
 include/linux/lsm_hook_defs.h |  3 +++
 include/linux/security.h      | 11 +++++++++++
 kernel/bpf/bpf_lsm.c          |  2 ++
 kernel/bpf/token.c            |  6 ++++++
 security/security.c           | 28 ++++++++++++++++++++++++++++
 6 files changed, 53 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c87af564f464..dfcac60f1857 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1585,6 +1585,9 @@ struct bpf_token {
 	u64 allowed_maps;
 	u64 allowed_progs;
 	u64 allowed_attachs;
+#ifdef CONFIG_SECURITY
+	void *security;
+#endif
 };
 
 struct bpf_struct_ops_value;
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 0adfb136521a..d776c9b7b856 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -404,6 +404,9 @@ LSM_HOOK(void, LSM_RET_VOID, bpf_map_free, struct bpf_map *map)
 LSM_HOOK(int, 0, bpf_prog_load, struct bpf_prog *prog, union bpf_attr *attr,
 	 struct bpf_token *token)
 LSM_HOOK(void, LSM_RET_VOID, bpf_prog_free, struct bpf_prog *prog)
+LSM_HOOK(int, 0, bpf_token_create, struct bpf_token *token, union bpf_attr *attr,
+	 struct path *path)
+LSM_HOOK(void, LSM_RET_VOID, bpf_token_free, struct bpf_token *token)
 #endif /* CONFIG_BPF_SYSCALL */
 
 LSM_HOOK(int, 0, locked_down, enum lockdown_reason what)
diff --git a/include/linux/security.h b/include/linux/security.h
index 59c5fab2c4d6..b9cb1446bb78 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2031,6 +2031,9 @@ extern void security_bpf_map_free(struct bpf_map *map);
 extern int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
 				  struct bpf_token *token);
 extern void security_bpf_prog_free(struct bpf_prog *prog);
+extern int security_bpf_token_create(struct bpf_token *token, union bpf_attr *attr,
+				     struct path *path);
+extern void security_bpf_token_free(struct bpf_token *token);
 #else
 static inline int security_bpf(int cmd, union bpf_attr *attr,
 					     unsigned int size)
@@ -2065,6 +2068,14 @@ static inline int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *
 
 static inline void security_bpf_prog_free(struct bpf_prog *prog)
 { }
+
+static inline int security_bpf_token_create(struct bpf_token *token, union bpf_attr *attr,
+				     struct path *path)
+{
+	return 0;
+}
+static inline void security_bpf_token_free(struct bpf_token *token)
+{ }
 #endif /* CONFIG_SECURITY */
 #endif /* CONFIG_BPF_SYSCALL */
 
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 9e4e615f11eb..2a019528953e 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -265,6 +265,8 @@ BTF_ID(func, bpf_lsm_bpf_map_free)
 BTF_ID(func, bpf_lsm_bpf_prog)
 BTF_ID(func, bpf_lsm_bpf_prog_load)
 BTF_ID(func, bpf_lsm_bpf_prog_free)
+BTF_ID(func, bpf_lsm_bpf_token_create)
+BTF_ID(func, bpf_lsm_bpf_token_free)
 BTF_ID(func, bpf_lsm_bprm_check_security)
 BTF_ID(func, bpf_lsm_bprm_committed_creds)
 BTF_ID(func, bpf_lsm_bprm_committing_creds)
diff --git a/kernel/bpf/token.c b/kernel/bpf/token.c
index d4e0cc8075d3..18fd1e04f92d 100644
--- a/kernel/bpf/token.c
+++ b/kernel/bpf/token.c
@@ -7,6 +7,7 @@
 #include <linux/idr.h>
 #include <linux/namei.h>
 #include <linux/user_namespace.h>
+#include <linux/security.h>
 
 bool bpf_token_capable(const struct bpf_token *token, int cap)
 {
@@ -28,6 +29,7 @@ void bpf_token_inc(struct bpf_token *token)
 
 static void bpf_token_free(struct bpf_token *token)
 {
+	security_bpf_token_free(token);
 	put_user_ns(token->userns);
 	kvfree(token);
 }
@@ -183,6 +185,10 @@ int bpf_token_create(union bpf_attr *attr)
 	token->allowed_progs = mnt_opts->delegate_progs;
 	token->allowed_attachs = mnt_opts->delegate_attachs;
 
+	err = security_bpf_token_create(token, attr, &path);
+	if (err)
+		goto out_token;
+
 	fd = get_unused_fd_flags(O_CLOEXEC);
 	if (fd < 0) {
 		err = fd;
diff --git a/security/security.c b/security/security.c
index 145e8082b9a6..83a2403b7261 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5201,6 +5201,23 @@ int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
 	return call_int_hook(bpf_prog_load, 0, prog, attr, token);
 }
 
+/**
+ * security_bpf_token_create() - Check if creating of BPF token is allowed
+ * @token BPF token object
+ * @attr: BPF syscall attributes used to create BPF token
+ * @path: path pointing to BPF FS mount point from which BPF token is created
+ *
+ * Do a check when the kernel instantiates a new BPF token object from BPF FS
+ * instance. This is also the point where LSM blob can be allocated for LSMs.
+ *
+ * Return: Returns 0 on success, error on failure.
+ */
+int security_bpf_token_create(struct bpf_token *token, union bpf_attr *attr,
+			      struct path *path)
+{
+	return call_int_hook(bpf_token_create, 0, token, attr, path);
+}
+
 /**
  * security_bpf_map_free() - Free a bpf map's LSM blob
  * @map: bpf map
@@ -5222,6 +5239,17 @@ void security_bpf_prog_free(struct bpf_prog *prog)
 {
 	call_void_hook(bpf_prog_free, prog);
 }
+
+/**
+ * security_bpf_token_free() - Free a BPF token's LSM blob
+ * @token: BPF token struct
+ *
+ * Clean up the security information stored inside BPF token.
+ */
+void security_bpf_token_free(struct bpf_token *token)
+{
+	call_void_hook(bpf_token_free, token);
+}
 #endif /* CONFIG_BPF_SYSCALL */
 
 /**
-- 
2.34.1