Add selftest cases that validate bpftool's expected behavior when accessing maps protected from modification via security_bpf_map.
The test includes a BPF program attached to security_bpf_map with two maps: - A protected map that only allows read-only access - An unprotected map that allows full access
The test script attaches the BPF program to security_bpf_map and verifies that for the bpftool map command: - Read access works on both maps - Write access fails on the protected map - Write access succeeds on the unprotected map - These behaviors remain consistent when the maps are pinned
Signed-off-by: Slava Imameev slava.imameev@crowdstrike.com --- Changes in v2: - fix for a test compilation error: "conflicting types for 'bpf_fentry_test1'" --- --- tools/testing/selftests/bpf/Makefile | 1 + .../selftests/bpf/progs/security_bpf_map.c | 56 +++++ .../testing/selftests/bpf/test_bpftool_map.sh | 208 ++++++++++++++++++ 3 files changed, 265 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/security_bpf_map.c create mode 100755 tools/testing/selftests/bpf/test_bpftool_map.sh
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index cf5ed3bee573..731a86407799 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -109,6 +109,7 @@ TEST_PROGS := test_kmod.sh \ test_xdping.sh \ test_bpftool_build.sh \ test_bpftool.sh \ + test_bpftool_map.sh \ test_bpftool_metadata.sh \ test_doc_build.sh \ test_xsk.sh \ diff --git a/tools/testing/selftests/bpf/progs/security_bpf_map.c b/tools/testing/selftests/bpf/progs/security_bpf_map.c new file mode 100644 index 000000000000..09048c096ee4 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/security_bpf_map.c @@ -0,0 +1,56 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include "vmlinux.h" +#include <bpf/bpf_tracing.h> +#include <bpf/bpf_helpers.h> + +char _license[] SEC("license") = "GPL"; + +#define EPERM 1 /* Operation not permitted */ + +/* From include/linux/mm.h. */ +#define FMODE_WRITE 0x2 + +struct map; + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __type(key, __u32); + __type(value, __u32); + __uint(max_entries, 1); +} prot_map SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __type(key, __u32); + __type(value, __u32); + __uint(max_entries, 1); +} not_prot_map SEC(".maps"); + +SEC("fmod_ret/security_bpf_map") +int BPF_PROG(fmod_bpf_map, struct bpf_map *map, int fmode) +{ + if (map == &prot_map) { + /* Allow read-only access */ + if (fmode & FMODE_WRITE) + return -EPERM; + } + + return 0; +} + +/* + * This program keeps references to maps. This is needed to prevent + * optimizing them out. + */ +SEC("fentry/bpf_fentry_test1") +int BPF_PROG(bpf_map_test0, int a) +{ + __u32 key = 0; + __u32 val1 = a; + __u32 val2 = a + 1; + + bpf_map_update_elem(&prot_map, &key, &val1, BPF_ANY); + bpf_map_update_elem(¬_prot_map, &key, &val2, BPF_ANY); + return 0; +} diff --git a/tools/testing/selftests/bpf/test_bpftool_map.sh b/tools/testing/selftests/bpf/test_bpftool_map.sh new file mode 100755 index 000000000000..c7c7f3d2071e --- /dev/null +++ b/tools/testing/selftests/bpf/test_bpftool_map.sh @@ -0,0 +1,208 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 + +# Kselftest framework requirement - SKIP code is 4. +ksft_skip=4 + +PROTECTED_MAP_NAME="prot_map" +NOT_PROTECTED_MAP_NAME="not_prot_map" +BPF_FILE="security_bpf_map.bpf.o" +TESTNAME="security_bpf_map" +BPF_FS=$(awk '$3 == "bpf" {print $2; exit}' /proc/mounts) +BPF_DIR="$BPF_FS/test_$TESTNAME" +SCRIPT_DIR=$(dirname $(realpath "$0")) +BPF_FILE_PATH="$SCRIPT_DIR/$BPF_FILE" +# Assume the script is located under tools/testing/selftests/bpf/ +KDIR_ROOT_DIR=$(realpath "$SCRIPT_DIR"/../../../../) + +_cleanup() +{ + set +eu + [ -d "$TMPDIR" ] && rm -rf "$TMPDIR" 2> /dev/null + [ -d "$BPF_DIR" ] && rm -rf "$BPF_DIR" 2> /dev/null +} + +cleanup_skip() +{ + echo "selftests: $TESTNAME [SKIP]" + _cleanup + + exit $ksft_skip +} + +cleanup() +{ + if [ "$?" = 0 ]; then + echo "selftests: $TESTNAME [PASS]" + else + echo "selftests: $TESTNAME [FAILED]" + fi + _cleanup +} + +# Parameters: +# $1: The top of kernel repository +# $2: Output directory +build_bpftool() +{ + local kdir_root_dir="$1" + local output_dir="$2" + local pwd="$(pwd)" + local ncpus=1 + + echo Building bpftool ... + + #We want to start build from the top of kernel repository. + cd "$kdir_root_dir" + if [ ! -e tools/bpf/bpftool/Makefile ]; then + echo bpftool files not found + exit $ksft_skip + fi + + # Determine the number of CPUs for parallel compilation + if command -v nproc >/dev/null 2>&1; then + ncpus=$(nproc) + fi + + make -C tools/bpf/bpftool -s -j"$ncpus" OUTPUT="$output_dir"/ >/dev/null + echo ... finished building bpftool + cd "$pwd" +} + +# Function to test map access with configurable write expectations +# Parameters: +# $1: Map name +# $2: Whether write should succeed (true/false) +# $3: bpftool path +# $4: BPF_DIR +test_map_access() { + local map_name="$1" + local write_should_succeed="$2" + local bpftool_path="$3" + local pin_path="$4/${map_name}_pinned" + local key="0 0 0 0" + local value="1 1 1 1" + + echo "Testing access to map: $map_name" + + # Test read access to the map + if "$bpftool_path" map lookup name "$map_name" key $key; then + echo " Read access to $map_name succeeded" + else + echo " Read access to $map_name failed" + exit 1 + fi + + # Test write access to the map + if "$bpftool_path" map update name "$map_name" key $key value $value; then + if [ "$write_should_succeed" = "true" ]; then + echo " Write access to $map_name succeeded as expected" + else + echo " Write access to $map_name succeeded but should have failed" + exit 1 + fi + else + if [ "$write_should_succeed" = "true" ]; then + echo " Write access to $map_name failed but should have succeeded" + exit 1 + else + echo " Write access to $map_name failed as expected" + fi + fi + + # Pin the map to the BPF filesystem + "$bpftool_path" map pin name "$map_name" "$pin_path" + if [ -e "$pin_path" ]; then + echo " Successfully pinned $map_name to $pin_path" + else + echo " Failed to pin $map_name" + exit 1 + fi + + # Test read access to the pinned map + if "$bpftool_path" map lookup pinned "$pin_path" key $key; then + echo " Read access to pinned $map_name succeeded" + else + echo " Read access to pinned $map_name failed" + exit 1 + fi + + # Test write access to the pinned map + if "$bpftool_path" map update pinned "$pin_path" key $key value $value; then + if [ "$write_should_succeed" = "true" ]; then + echo " Write access to pinned $map_name succeeded as expected" + else + echo " Write access to pinned $map_name succeeded but should have failed" + exit 1 + fi + else + if [ "$write_should_succeed" = "true" ]; then + echo " Write access to pinned $map_name failed but should have succeeded" + exit 1 + else + echo " Write access to pinned $map_name failed as expected" + fi + fi + + echo " Finished testing $map_name" + echo +} + +check_root_privileges() { + if [ $(id -u) -ne 0 ]; then + echo "Need root privileges" + exit $ksft_skip + fi +} + +check_bpffs() { + if [ -z "$BPF_FS" ]; then + echo "Could not run test without bpffs mounted" + exit $ksft_skip + fi +} + +create_tmp_dir() { + TMPDIR=$(mktemp -d) + if [ $? -ne 0 ] || [ ! -d "$TMPDIR" ]; then + echo "Failed to create temporary directory" + exit $ksft_skip + fi +} + +locate_or_build_bpftool() { + if ! bpftool version > /dev/null 2>&1; then + build_bpftool "$KDIR_ROOT_DIR" "$TMPDIR" + BPFTOOL_PATH="$TMPDIR"/bpftool + else + echo "Using bpftool from PATH" + BPFTOOL_PATH="bpftool" + fi +} + +set -eu + +trap cleanup_skip EXIT + +check_root_privileges + +check_bpffs + +create_tmp_dir + +locate_or_build_bpftool + +mkdir "$BPF_DIR" + +trap cleanup EXIT + +# Load and attach the BPF programs to control maps access +"$BPFTOOL_PATH" prog loadall "$BPF_FILE_PATH" "$BPF_DIR"/prog autoattach + +# Test protected map (write should fail) +test_map_access "$PROTECTED_MAP_NAME" "false" "$BPFTOOL_PATH" "$BPF_DIR" + +# Test not protected map (write should succeed) +test_map_access "$NOT_PROTECTED_MAP_NAME" "true" "$BPFTOOL_PATH" "$BPF_DIR" + +exit 0