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>

7 files changed, 11 insertions, 10 deletions

diff --git a/tools/testing/selftests/bpf/progs/rcu_read_lock.c b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
index 5cf1ae637ec7..43637ee2cdcd 100644
--- a/tools/testing/selftests/bpf/progs/rcu_read_lock.c
+++ b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
@@ -242,7 +242,8 @@ out:
 }
 
 SEC("?lsm.s/bpf")
-int BPF_PROG(inproper_sleepable_kfunc, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(inproper_sleepable_kfunc, int cmd, union bpf_attr *attr, unsigned int size,
+	     bool kernel)
 {
 	struct bpf_key *bkey;
 
diff --git a/tools/testing/selftests/bpf/progs/test_cgroup1_hierarchy.c b/tools/testing/selftests/bpf/progs/test_cgroup1_hierarchy.c
index 44628865fe1d..4fee0fdc7607 100644
--- a/tools/testing/selftests/bpf/progs/test_cgroup1_hierarchy.c
+++ b/tools/testing/selftests/bpf/progs/test_cgroup1_hierarchy.c
@@ -51,13 +51,13 @@ out:
 }
 
 SEC("lsm/bpf")
-int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	return bpf_link_create_verify(cmd);
 }
 
 SEC("lsm.s/bpf")
-int BPF_PROG(lsm_s_run, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(lsm_s_run, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	return bpf_link_create_verify(cmd);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
index cd4d752bd089..061befb004c2 100644
--- a/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
+++ b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
@@ -36,7 +36,7 @@ char _license[] SEC("license") = "GPL";
 
 SEC("?lsm.s/bpf")
 __failure __msg("cannot pass in dynptr at an offset=-8")
-int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	unsigned long val;
 
@@ -46,7 +46,7 @@ int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size)
 
 SEC("?lsm.s/bpf")
 __failure __msg("arg#0 expected pointer to stack or const struct bpf_dynptr")
-int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	unsigned long val = 0;
 
@@ -55,7 +55,7 @@ int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr, unsigned int size)
 }
 
 SEC("lsm.s/bpf")
-int BPF_PROG(dynptr_data_null, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(dynptr_data_null, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	struct bpf_key *trusted_keyring;
 	struct bpf_dynptr ptr;
diff --git a/tools/testing/selftests/bpf/progs/test_lookup_key.c b/tools/testing/selftests/bpf/progs/test_lookup_key.c
index c73776990ae3..cdbbb12f1491 100644
--- a/tools/testing/selftests/bpf/progs/test_lookup_key.c
+++ b/tools/testing/selftests/bpf/progs/test_lookup_key.c
@@ -23,7 +23,7 @@ extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
 extern void bpf_key_put(struct bpf_key *key) __ksym;
 
 SEC("lsm.s/bpf")
-int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	struct bpf_key *bkey;
 	__u32 pid;
diff --git a/tools/testing/selftests/bpf/progs/test_ptr_untrusted.c b/tools/testing/selftests/bpf/progs/test_ptr_untrusted.c
index 2fdc44e76624..89b0cd5a3e06 100644
--- a/tools/testing/selftests/bpf/progs/test_ptr_untrusted.c
+++ b/tools/testing/selftests/bpf/progs/test_ptr_untrusted.c
@@ -7,7 +7,7 @@
 char tp_name[128];
 
 SEC("lsm.s/bpf")
-int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	switch (cmd) {
 	case BPF_RAW_TRACEPOINT_OPEN:
diff --git a/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
index 7e750309ce27..0b74b8bd22e8 100644
--- a/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
+++ b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
@@ -49,7 +49,7 @@ out:
 }
 
 SEC("lsm.s/bpf")
-int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	struct cgroup *cgrp = NULL;
 	struct task_struct *task;
diff --git a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
index 12034a73ee2d..e96d09e11115 100644
--- a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
+++ b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
@@ -37,7 +37,7 @@ struct {
 char _license[] SEC("license") = "GPL";
 
 SEC("lsm.s/bpf")
-int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
+int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
 	struct bpf_dynptr data_ptr, sig_ptr;
 	struct data *data_val;