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selftests/bpf: Add tests for tail calls with locks and refs

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Add failure tests to ensure bugs don't slip through for tail calls and
lingering locks, RCU sections, preemption disabled sections, and
references prevent tail calls.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241103225940.1408302-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi
2024-11-03 14:59:40 -08:00
committed by Alexei Starovoitov
parent d402755ced
commit 711df091de
2 changed files with 72 additions and 0 deletions
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8
tools/testing/selftests/bpf/prog_tests/tailcalls.c
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@@ -7,6 +7,7 @@
#include "tailcall_bpf2bpf_hierarchy3.skel.h"
#include "tailcall_freplace.skel.h"
#include "tc_bpf2bpf.skel.h"
#include "tailcall_fail.skel.h"
/* test_tailcall_1 checks basic functionality by patching multiple locations
* in a single program for a single tail call slot with nop->jmp, jmp->nop
@@ -1646,6 +1647,11 @@ out:
tc_bpf2bpf__destroy(tc_skel);
}
static void test_tailcall_failure()
{
RUN_TESTS(tailcall_fail);
}
void test_tailcalls(void)
{
if (test__start_subtest("tailcall_1"))
@@ -1698,4 +1704,6 @@ void test_tailcalls(void)
test_tailcall_freplace();
if (test__start_subtest("tailcall_bpf2bpf_freplace"))
test_tailcall_bpf2bpf_freplace();
if (test__start_subtest("tailcall_failure"))
test_tailcall_failure();
}

64
tools/testing/selftests/bpf/progs/tailcall_fail.c Normal file
View File

@@ -0,0 +1,64 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
#include <vmlinux.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_core_read.h>
#include "bpf_misc.h"
#include "bpf_experimental.h"
extern void bpf_rcu_read_lock(void) __ksym;
extern void bpf_rcu_read_unlock(void) __ksym;
#define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8)))
private(A) struct bpf_spin_lock lock;
struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(max_entries, 3);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");
SEC("?tc")
__failure __msg("function calls are not allowed while holding a lock")
int reject_tail_call_spin_lock(struct __sk_buff *ctx)
{
bpf_spin_lock(&lock);
bpf_tail_call_static(ctx, &jmp_table, 0);
return 0;
}
SEC("?tc")
__failure __msg("tail_call cannot be used inside bpf_rcu_read_lock-ed region")
int reject_tail_call_rcu_lock(struct __sk_buff *ctx)
{
bpf_rcu_read_lock();
bpf_tail_call_static(ctx, &jmp_table, 0);
bpf_rcu_read_unlock();
return 0;
}
SEC("?tc")
__failure __msg("tail_call cannot be used inside bpf_preempt_disable-ed region")
int reject_tail_call_preempt_lock(struct __sk_buff *ctx)
{
bpf_guard_preempt();
bpf_tail_call_static(ctx, &jmp_table, 0);
return 0;
}
SEC("?tc")
__failure __msg("tail_call would lead to reference leak")
int reject_tail_call_ref(struct __sk_buff *ctx)
{
struct foo { int i; } *p;
p = bpf_obj_new(typeof(*p));
bpf_tail_call_static(ctx, &jmp_table, 0);
return 0;
}
char _license[] SEC("license") = "GPL";