bpf/progs/verifier_global_subprogs.c

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */

#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include "bpf_misc.h"
#include "xdp_metadata.h"
#include "bpf_kfuncs.h"

/* The compiler may be able to detect the access to uninitialized
   memory in the routines performing out of bound memory accesses and
   emit warnings about it.  This is the case of GCC. */
#if !defined(__clang__)
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif

int arr[1];
int unkn_idx;
const volatile bool call_dead_subprog = false;

__noinline long global_bad(void)
{
	return arr[unkn_idx]; /* BOOM */
}

__noinline long global_good(void)
{
	return arr[0];
}

__noinline long global_calls_bad(void)
{
	return global_good() + global_bad() /* does BOOM indirectly */;
}

__noinline long global_calls_good_only(void)
{
	return global_good();
}

__noinline long global_dead(void)
{
	return arr[0] * 2;
}

SEC("?raw_tp")
__success __log_level(2)
/* main prog is validated completely first */
__msg("('global_calls_good_only') is global and assumed valid.")
/* eventually global_good() is transitively validated as well */
__msg("Validating global_good() func")
__msg("('global_good') is safe for any args that match its prototype")
int chained_global_func_calls_success(void)
{
	int sum = 0;

	if (call_dead_subprog)
		sum += global_dead();
	return global_calls_good_only() + sum;
}

SEC("?raw_tp")
__failure __log_level(2)
/* main prog validated successfully first */
__msg("('global_calls_bad') is global and assumed valid.")
/* eventually we validate global_bad() and fail */
__msg("Validating global_bad() func")
__msg("math between map_value pointer and register") /* BOOM */
int chained_global_func_calls_bad(void)
{
	return global_calls_bad();
}

/* do out of bounds access forcing verifier to fail verification if this
 * global func is called
 */
__noinline int global_unsupp(const int *mem)
{
	if (!mem)
		return 0;
	return mem[100]; /* BOOM */
}

const volatile bool skip_unsupp_global = true;

SEC("?raw_tp")
__success
int guarded_unsupp_global_called(void)
{
	if (!skip_unsupp_global)
		return global_unsupp(NULL);
	return 0;
}

SEC("?raw_tp")
__failure __log_level(2)
__msg("Func#1 ('global_unsupp') is global and assumed valid.")
__msg("Validating global_unsupp() func#1...")
__msg("value is outside of the allowed memory range")
int unguarded_unsupp_global_called(void)
{
	int x = 0;

	return global_unsupp(&x);
}

long stack[128];

__weak int subprog_nullable_ptr_bad(int *p)
{
	return (*p) * 2; /* bad, missing null check */
}

SEC("?raw_tp")
__failure __log_level(2)
__msg("invalid mem access 'mem_or_null'")
int arg_tag_nullable_ptr_fail(void *ctx)
{
	int x = 42;

	return subprog_nullable_ptr_bad(&x);
}

typedef struct {
	int x;
} user_struct_t;

__noinline __weak int subprog_user_anon_mem(user_struct_t *t)
{
	return t ? t->x : 0;
}

SEC("?tracepoint")
__failure __log_level(2)
__msg("invalid bpf_context access")
__msg("Caller passes invalid args into func#1 ('subprog_user_anon_mem')")
int anon_user_mem_invalid(void *ctx)
{
	/* can't pass PTR_TO_CTX as user memory */
	return subprog_user_anon_mem(ctx);
}

SEC("?tracepoint")
__success __log_level(2)
__msg("Func#1 ('subprog_user_anon_mem') is safe for any args that match its prototype")
int anon_user_mem_valid(void *ctx)
{
	user_struct_t t = { .x = 42 };

	return subprog_user_anon_mem(&t);
}

__noinline __weak int subprog_nonnull_ptr_good(int *p1 __arg_nonnull, int *p2 __arg_nonnull)
{
	return (*p1) * (*p2); /* good, no need for NULL checks */
}

int x = 47;

SEC("?raw_tp")
__success __log_level(2)
int arg_tag_nonnull_ptr_good(void *ctx)
{
	int y = 74;

	return subprog_nonnull_ptr_good(&x, &y);
}

/* this global subprog can be now called from many types of entry progs, each
 * with different context type
 */
__weak int subprog_ctx_tag(void *ctx __arg_ctx)
{
	return bpf_get_stack(ctx, stack, sizeof(stack), 0);
}

__weak int raw_tp_canonical(struct bpf_raw_tracepoint_args *ctx __arg_ctx)
{
	return 0;
}

__weak int raw_tp_u64_array(u64 *ctx __arg_ctx)
{
	return 0;
}

SEC("?raw_tp")
__success __log_level(2)
int arg_tag_ctx_raw_tp(void *ctx)
{
	return subprog_ctx_tag(ctx) + raw_tp_canonical(ctx) + raw_tp_u64_array(ctx);
}

SEC("?raw_tp.w")
__success __log_level(2)
int arg_tag_ctx_raw_tp_writable(void *ctx)
{
	return subprog_ctx_tag(ctx) + raw_tp_canonical(ctx) + raw_tp_u64_array(ctx);
}

SEC("?tp_btf/sys_enter")
__success __log_level(2)
int arg_tag_ctx_raw_tp_btf(void *ctx)
{
	return subprog_ctx_tag(ctx) + raw_tp_canonical(ctx) + raw_tp_u64_array(ctx);
}

struct whatever { };

__weak int tp_whatever(struct whatever *ctx __arg_ctx)
{
	return 0;
}

SEC("?tp")
__success __log_level(2)
int arg_tag_ctx_tp(void *ctx)
{
	return subprog_ctx_tag(ctx) + tp_whatever(ctx);
}

__weak int kprobe_subprog_pt_regs(struct pt_regs *ctx __arg_ctx)
{
	return 0;
}

__weak int kprobe_subprog_typedef(bpf_user_pt_regs_t *ctx __arg_ctx)
{
	return 0;
}

SEC("?kprobe")
__success __log_level(2)
int arg_tag_ctx_kprobe(void *ctx)
{
	return subprog_ctx_tag(ctx) +
	       kprobe_subprog_pt_regs(ctx) +
	       kprobe_subprog_typedef(ctx);
}

__weak int perf_subprog_regs(
#if defined(bpf_target_riscv)
	struct user_regs_struct *ctx __arg_ctx
#elif defined(bpf_target_s390)
	/* user_pt_regs typedef is anonymous struct, so only `void *` works */
	void *ctx __arg_ctx
#elif defined(bpf_target_loongarch) || defined(bpf_target_arm64) || defined(bpf_target_powerpc)
	struct user_pt_regs *ctx __arg_ctx
#else
	struct pt_regs *ctx __arg_ctx
#endif
)
{
	return 0;
}

__weak int perf_subprog_typedef(bpf_user_pt_regs_t *ctx __arg_ctx)
{
	return 0;
}

__weak int perf_subprog_canonical(struct bpf_perf_event_data *ctx __arg_ctx)
{
	return 0;
}

SEC("?perf_event")
__success __log_level(2)
int arg_tag_ctx_perf(void *ctx)
{
	return subprog_ctx_tag(ctx) +
	       perf_subprog_regs(ctx) +
	       perf_subprog_typedef(ctx) +
	       perf_subprog_canonical(ctx);
}

__weak int iter_subprog_void(void *ctx __arg_ctx)
{
	return 0;
}

__weak int iter_subprog_typed(struct bpf_iter__task *ctx __arg_ctx)
{
	return 0;
}

SEC("?iter/task")
__success __log_level(2)
int arg_tag_ctx_iter_task(struct bpf_iter__task *ctx)
{
	return (iter_subprog_void(ctx) + iter_subprog_typed(ctx)) & 1;
}

__weak int tracing_subprog_void(void *ctx __arg_ctx)
{
	return 0;
}

__weak int tracing_subprog_u64(u64 *ctx __arg_ctx)
{
	return 0;
}

int acc;

SEC("?fentry/" SYS_PREFIX "sys_nanosleep")
__success __log_level(2)
int BPF_PROG(arg_tag_ctx_fentry)
{
	acc += tracing_subprog_void(ctx) + tracing_subprog_u64(ctx);
	return 0;
}

SEC("?fexit/" SYS_PREFIX "sys_nanosleep")
__success __log_level(2)
int BPF_PROG(arg_tag_ctx_fexit)
{
	acc += tracing_subprog_void(ctx) + tracing_subprog_u64(ctx);
	return 0;
}

SEC("?fmod_ret/" SYS_PREFIX "sys_nanosleep")
__success __log_level(2)
int BPF_PROG(arg_tag_ctx_fmod_ret)
{
	return tracing_subprog_void(ctx) + tracing_subprog_u64(ctx);
}

SEC("?lsm/bpf")
__success __log_level(2)
int BPF_PROG(arg_tag_ctx_lsm)
{
	return tracing_subprog_void(ctx) + tracing_subprog_u64(ctx);
}

SEC("?struct_ops/test_1")
__success __log_level(2)
int BPF_PROG(arg_tag_ctx_struct_ops)
{
	return tracing_subprog_void(ctx) + tracing_subprog_u64(ctx);
}

SEC(".struct_ops")
struct bpf_dummy_ops dummy_1 = {
	.test_1 = (void *)arg_tag_ctx_struct_ops,
};

SEC("?syscall")
__success __log_level(2)
int arg_tag_ctx_syscall(void *ctx)
{
	return tracing_subprog_void(ctx) + tracing_subprog_u64(ctx) + tp_whatever(ctx);
}

__weak int subprog_dynptr(struct bpf_dynptr *dptr)
{
	long *d, t, buf[1] = {};

	d = bpf_dynptr_data(dptr, 0, sizeof(long));
	if (!d)
		return 0;

	t = *d + 1;

	d = bpf_dynptr_slice(dptr, 0, &buf, sizeof(long));
	if (!d)
		return t;

	t = *d + 2;

	return t;
}

SEC("?xdp")
__success __log_level(2)
int arg_tag_dynptr(struct xdp_md *ctx)
{
	struct bpf_dynptr dptr;

	bpf_dynptr_from_xdp(ctx, 0, &dptr);

	return subprog_dynptr(&dptr);
}

char _license[] SEC("license") = "GPL";