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selftests/bpf: Test that exclusive maps are rejected as iter targets

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Add a subtest to map_excl that creates an exclusive map and verifies a
bpf_map_elem iterator cannot be attached to it, which would otherwise
let an unrelated program read and overwrite the map's contents through
the iterator's writable value buffer.

  # LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh -- ./test_progs -t map_excl
  [...]
  ./test_progs -t map_excl
  [    1.704382] bpf_testmod: loading out-of-tree module taints kernel.
  [    1.706068] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
  #215/1   map_excl/map_excl_allowed:OK
  #215/2   map_excl/map_excl_denied:OK
  #215/3   map_excl/map_excl_no_map_in_map:OK
  #215/4   map_excl/map_excl_no_map_iter:OK
  #215     map_excl:OK
  Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260602133052.423725-5-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2026-06-02 15:30:52 +02:00 committed by Alexei Starovoitov
parent 082c412097
commit 8dedd34122
1 changed files with 39 additions and 0 deletions
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39
tools/testing/selftests/bpf/prog_tests/map_excl.c
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@ -7,6 +7,7 @@
#include <bpf/btf.h>
#include "map_excl.skel.h"
#include "bpf_iter_bpf_array_map.skel.h"
#ifndef SHA256_DIGEST_SIZE
#define SHA256_DIGEST_SIZE 32
@ -89,6 +90,42 @@ static void test_map_excl_no_map_in_map(void)
close(excl_fd);
}
static void test_map_excl_no_map_iter(void)
{
__u8 hash[SHA256_DIGEST_SIZE] = {};
LIBBPF_OPTS(bpf_map_create_opts, excl_opts,
.excl_prog_hash = hash,
.excl_prog_hash_size = sizeof(hash));
DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
struct bpf_iter_bpf_array_map *skel = NULL;
union bpf_iter_link_info linfo;
struct bpf_link *link;
int excl_fd;
excl_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "excl_iter", 4, 8, 3, &excl_opts);
if (!ASSERT_OK_FD(excl_fd, "create exclusive map"))
return;
skel = bpf_iter_bpf_array_map__open_and_load();
if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_array_map__open_and_load"))
goto out;
memset(&linfo, 0, sizeof(linfo));
linfo.map.map_fd = excl_fd;
opts.link_info = &linfo;
opts.link_info_len = sizeof(linfo);
link = bpf_program__attach_iter(skel->progs.dump_bpf_array_map, &opts);
if (!ASSERT_ERR_PTR(link, "reject exclusive map as iter target")) {
bpf_link__destroy(link);
goto out;
}
ASSERT_EQ(libbpf_get_error(link), -EPERM, "iter attach errno");
out:
bpf_iter_bpf_array_map__destroy(skel);
close(excl_fd);
}
void test_map_excl(void)
{
if (test__start_subtest("map_excl_allowed"))
@ -97,4 +134,6 @@ void test_map_excl(void)
test_map_excl_denied();
if (test__start_subtest("map_excl_no_map_in_map"))
test_map_excl_no_map_in_map();
if (test__start_subtest("map_excl_no_map_iter"))
test_map_excl_no_map_iter();
}