Commit 82bbe133 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add test for passing in uninit mtu_len 



Add a small test to pass an uninitialized mtu_len to the bpf_check_mtu()
helper to probe whether the verifier rejects it under !CAP_PERFMON.

  # ./vmtest.sh -- ./test_progs -t verifier_mtu
  [...]
  ./test_progs -t verifier_mtu
  [    1.414712] tsc: Refined TSC clocksource calibration: 3407.993 MHz
  [    1.415327] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fcd52370, max_idle_ns: 440795242006 ns
  [    1.416463] clocksource: Switched to clocksource tsc
  [    1.429842] bpf_testmod: loading out-of-tree module taints kernel.
  [    1.430283] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
  #510/1   verifier_mtu/uninit/mtu: write rejected:OK
  #510     verifier_mtu:OK
  Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241021152809.33343-5-daniel@iogearbox.net


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent baa802d2

tools/testing/selftests/bpf/prog_tests/verifier.c

+19 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ 
#include "verifier_masking.skel.h"

#include "verifier_meta_access.skel.h"

#include "verifier_movsx.skel.h"

#include "verifier_mtu.skel.h"

#include "verifier_netfilter_ctx.skel.h"

#include "verifier_netfilter_retcode.skel.h"

#include "verifier_bpf_fastcall.skel.h"
@@ -223,6 +224,24 @@ void test_verifier_xdp_direct_packet_access(void) { RUN(verifier_xdp_direct_pack 
void test_verifier_bits_iter(void) { RUN(verifier_bits_iter); }

void test_verifier_lsm(void)                  { RUN(verifier_lsm); }



void test_verifier_mtu(void)

{

	__u64 caps = 0;

	int ret;



	/* In case CAP_BPF and CAP_PERFMON is not set */

	ret = cap_enable_effective(1ULL << CAP_BPF | 1ULL << CAP_NET_ADMIN, &caps);

	if (!ASSERT_OK(ret, "set_cap_bpf_cap_net_admin"))

		return;

	ret = cap_disable_effective(1ULL << CAP_SYS_ADMIN | 1ULL << CAP_PERFMON, NULL);

	if (!ASSERT_OK(ret, "disable_cap_sys_admin"))

		goto restore_cap;

	RUN(verifier_mtu);

restore_cap:

	if (caps)

		cap_enable_effective(caps, NULL);

}



static int init_test_val_map(struct bpf_object *obj, char *map_name)

{

	struct test_val value = {

tools/testing/selftests/bpf/progs/verifier_mtu.c

0 → 100644
+18 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include "bpf_misc.h"



SEC("tc/ingress")

__description("uninit/mtu: write rejected")

__failure __msg("invalid indirect read from stack")

int tc_uninit_mtu(struct __sk_buff *ctx)

{

	__u32 mtu;



	bpf_check_mtu(ctx, 0, &mtu, 0, 0);

	return TCX_PASS;

}



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