security: Propagate caller information in bpf hooks

Certain bpf syscall subcommands are available for usage from both
userspace and the kernel. LSM modules or eBPF gatekeeper programs may
need to take a different course of action depending on whether or not
a BPF syscall originated from the kernel or userspace.

Additionally, some of the bpf_attr struct fields contain pointers to
arbitrary memory. Currently the functionality to determine whether or
not a pointer refers to kernel memory or userspace memory is exposed
to the bpf verifier, but that information is missing from various LSM
hooks.

Here we augment the LSM hooks to provide this data, by simply passing
a boolean flag indicating whether or not the call originated in the
kernel, in any hook that contains a bpf_attr struct that corresponds
to a subcommand that may be called from the kernel.

Signed-off-by: Blaise Boscaccy <bboscaccy@linux.microsoft.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20250310221737.821889-2-bboscaccy@linux.microsoft.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 12 insertions, 9 deletions

diff --git a/security/security.c b/security/security.c
index 143561ebc3e8..c36948123258 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5627,6 +5627,7 @@ int security_audit_rule_match(struct lsm_prop *prop, u32 field, u32 op,
  * @cmd: command
  * @attr: bpf attribute
  * @size: size
+ * @kernel: whether or not call originated from kernel
  *
  * Do a initial check for all bpf syscalls after the attribute is copied into
  * the kernel. The actual security module can implement their own rules to
@@ -5634,9 +5635,9 @@ int security_audit_rule_match(struct lsm_prop *prop, u32 field, u32 op,
  *
  * Return: Returns 0 if permission is granted.
  */
-int security_bpf(int cmd, union bpf_attr *attr, unsigned int size)
+int security_bpf(int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
-	return call_int_hook(bpf, cmd, attr, size);
+	return call_int_hook(bpf, cmd, attr, size, kernel);
 }
 
 /**
@@ -5673,6 +5674,7 @@ int security_bpf_prog(struct bpf_prog *prog)
  * @map: BPF map object
  * @attr: BPF syscall attributes used to create BPF map
  * @token: BPF token used to grant user access
+ * @kernel: whether or not call originated from kernel
  *
  * Do a check when the kernel creates a new BPF map. This is also the
  * point where LSM blob is allocated for LSMs that need them.
@@ -5680,9 +5682,9 @@ int security_bpf_prog(struct bpf_prog *prog)
  * Return: Returns 0 on success, error on failure.
  */
 int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
-			    struct bpf_token *token)
+			    struct bpf_token *token, bool kernel)
 {
-	return call_int_hook(bpf_map_create, map, attr, token);
+	return call_int_hook(bpf_map_create, map, attr, token, kernel);
 }
 
 /**
@@ -5690,6 +5692,7 @@ int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
  * @prog: BPF program object
  * @attr: BPF syscall attributes used to create BPF program
  * @token: BPF token used to grant user access to BPF subsystem
+ * @kernel: whether or not call originated from kernel
  *
  * Perform an access control check when the kernel loads a BPF program and
  * allocates associated BPF program object. This hook is also responsible for
@@ -5698,9 +5701,9 @@ int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
  * Return: Returns 0 on success, error on failure.
  */
 int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
-			   struct bpf_token *token)
+			   struct bpf_token *token, bool kernel)
 {
-	return call_int_hook(bpf_prog_load, prog, attr, token);
+	return call_int_hook(bpf_prog_load, prog, attr, token, kernel);
 }
 
 /**
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 7b867dfec88b..71199d86fc97 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6866,7 +6866,7 @@ static int selinux_ib_alloc_security(void *ib_sec)
 
 #ifdef CONFIG_BPF_SYSCALL
 static int selinux_bpf(int cmd, union bpf_attr *attr,
-				     unsigned int size)
+		       unsigned int size, bool kernel)
 {
 	u32 sid = current_sid();
 	int ret;
@@ -6953,7 +6953,7 @@ static int selinux_bpf_prog(struct bpf_prog *prog)
 }
 
 static int selinux_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
-				  struct bpf_token *token)
+				  struct bpf_token *token, bool kernel)
 {
 	struct bpf_security_struct *bpfsec;
 
@@ -6976,7 +6976,7 @@ static void selinux_bpf_map_free(struct bpf_map *map)
 }
 
 static int selinux_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
-				 struct bpf_token *token)
+				 struct bpf_token *token, bool kernel)
 {
 	struct bpf_security_struct *bpfsec;