Merge branch 'security-propagate-caller-information-in-bpf-hooks'

Blaise Boscaccy says:

====================
While trying to implement an eBPF gatekeeper program, we ran into an
issue whereas the LSM hooks are missing some relevant data.

Certain subcommands passed to the bpf() syscall can be invoked from
either the kernel or userspace. Additionally, some fields in the
bpf_attr struct contain pointers, and depending on where the
subcommand was invoked, they could point to either user or kernel
memory. One example of this is the bpf_prog_load subcommand and its
fd_array. This data is made available and used by the verifier but not
made available to the LSM subsystem. This patchset simply exposes that
information to applicable LSM hooks.

Change list:
- v6 -> v7
  - use gettid/pid in lieu of getpid/tgid in test condition
- v5 -> v6
  - fix regression caused by is_kernel renaming
  - simplify test logic
- v4 -> v5
  - merge v4 selftest breakout patch back into a single patch
  - change "is_kernel" to "kernel"
  - add selftest using new kernel flag
- v3 -> v4
  - split out selftest changes into a separate patch
- v2 -> v3
  - reorder params so that the new boolean flag is the last param
  - fixup function signatures in bpf selftests
- v1 -> v2
  - Pass a boolean flag in lieu of bpfptr_t

Revisions:
- v6
  https://lore.kernel.org/bpf/20250308013314.719150-1-bboscaccy@linux.microsoft.com/
- v5
  https://lore.kernel.org/bpf/20250307213651.3065714-1-bboscaccy@linux.microsoft.com/
- v4
  https://lore.kernel.org/bpf/20250304203123.3935371-1-bboscaccy@linux.microsoft.com/
- v3
  https://lore.kernel.org/bpf/20250303222416.3909228-1-bboscaccy@linux.microsoft.com/
- v2
  https://lore.kernel.org/bpf/20250228165322.3121535-1-bboscaccy@linux.microsoft.com/
- v1
  https://lore.kernel.org/bpf/20250226003055.1654837-1-bboscaccy@linux.microsoft.com/
====================

Link: https://patch.msgid.link/20250310221737.821889-1-bboscaccy@linux.microsoft.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

9 files changed, 82 insertions, 10 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/kernel_flag.c b/tools/testing/selftests/bpf/prog_tests/kernel_flag.c
new file mode 100644
index 000000000000..a133354ac9bc
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/kernel_flag.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Microsoft */
+#include <test_progs.h>
+#include "kfunc_call_test.skel.h"
+#include "kfunc_call_test.lskel.h"
+#include "test_kernel_flag.skel.h"
+
+void test_kernel_flag(void)
+{
+	struct test_kernel_flag *lsm_skel;
+	struct kfunc_call_test *skel = NULL;
+	struct kfunc_call_test_lskel *lskel = NULL;
+	int ret;
+
+	lsm_skel = test_kernel_flag__open_and_load();
+	if (!ASSERT_OK_PTR(lsm_skel, "lsm_skel"))
+		return;
+
+	lsm_skel->bss->monitored_tid = gettid();
+
+	ret = test_kernel_flag__attach(lsm_skel);
+	if (!ASSERT_OK(ret, "test_kernel_flag__attach"))
+		goto close_prog;
+
+	/* Test with skel. This should pass the gatekeeper */
+	skel = kfunc_call_test__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel"))
+		goto close_prog;
+
+	/* Test with lskel. This should fail due to blocking kernel-based bpf() invocations */
+	lskel = kfunc_call_test_lskel__open_and_load();
+	if (!ASSERT_ERR_PTR(lskel, "lskel"))
+		goto close_prog;
+
+close_prog:
+	if (skel)
+		kfunc_call_test__destroy(skel);
+	if (lskel)
+		kfunc_call_test_lskel__destroy(lskel);
+
+	lsm_skel->bss->monitored_tid = 0;
+	test_kernel_flag__destroy(lsm_skel);
+}
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_kernel_flag.c b/tools/testing/selftests/bpf/progs/test_kernel_flag.c
new file mode 100644
index 000000000000..b45fab3be352
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_kernel_flag.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2025 Microsoft Corporation
+ *
+ * Author: Blaise Boscaccy <bboscaccy@linux.microsoft.com>
+ */
+
+#include "vmlinux.h"
+#include <errno.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+__u32 monitored_tid;
+
+SEC("lsm.s/bpf")
+int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
+{
+	__u32 tid;
+
+	tid = bpf_get_current_pid_tgid() & 0xFFFFFFFF;
+	if (!kernel || tid != monitored_tid)
+		return 0;
+	else
+		return -EINVAL;
+}
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;