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Wed, 12 Aug 2026 04:12:17 -0700 (PDT) Received: from dell-desktop ([2a02:587:4b5e:1100:7303:647d:7cc4:8552]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4997c9417bcsm54830855e9.4.2026.08.12.04.12.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Aug 2026 04:12:17 -0700 (PDT) From: Anastasios Papagiannis To: bpf@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, akpm@linux-foundation.org, david@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, kpsingh@kernel.org, matt@bobrowski.net, song@kernel.org, tasos.papagiannnis@gmail.com Subject: [PATCH bpf-next 3/3] selftests/bpf: Test linux_binprm user memory kfuncs Date: Wed, 12 Aug 2026 14:11:40 +0300 Message-ID: <20260812111140.7762-4-tasos.papagiannnis@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260812111140.7762-1-tasos.papagiannnis@gmail.com> References: <20260812111140.7762-1-tasos.papagiannnis@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This patch adds a sleepable BPF LSM program attached to bprm_check_security to test bpf_copy_from_user_bprm() and bpf_copy_from_user_bprm_str(). Starting at bprm->p, verify that bpf_copy_from_user_bprm() can copy the contiguous NUL-separated argument data. Then use bpf_copy_from_user_bprm_str() to read each argument separately, by advancing the offset based on the returned length. Signed-off-by: Anastasios Papagiannis --- .../bpf/prog_tests/copy_from_user_bprm.c | 52 +++++++++++++ .../selftests/bpf/progs/copy_from_user_bprm.c | 74 +++++++++++++++++++ 2 files changed, 126 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c create mode 100644 tools/testing/selftests/bpf/progs/copy_from_user_bprm.c diff --git a/tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c b/tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c new file mode 100644 index 000000000000..3d5080a3975e --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include + +#include + +#include "copy_from_user_bprm.skel.h" + +void test_copy_from_user_bprm(void) +{ + struct copy_from_user_bprm *skel; + pid_t child; + int status; + + skel = copy_from_user_bprm__open_and_load(); + if (!ASSERT_OK_PTR(skel, "open_and_load")) + return; + + if (!ASSERT_OK(copy_from_user_bprm__attach(skel), "attach")) + goto out; + + child = fork(); + if (!ASSERT_GE(child, 0, "fork")) + goto out; + + if (!child) { + char *const argv[] = { "first", "second-argument", NULL }; + + skel->bss->monitored_pid = getpid(); + execv("/bin/true", argv); + _exit(errno); + } + + if (!ASSERT_EQ(waitpid(child, &status, 0), child, "waitpid")) + goto out; + + if (ASSERT_TRUE(WIFEXITED(status), "child_exited")) + ASSERT_EQ(WEXITSTATUS(status), EPERM, "exec_errno"); + + ASSERT_EQ(skel->bss->bprm_argc, 2, "bprm_argc"); + ASSERT_EQ(skel->bss->invalid_flags_ret, -EINVAL, "invalid_flags_ret"); + ASSERT_EQ(skel->bss->copy_ret, 0, "copy_ret"); + ASSERT_EQ(skel->bss->str_arg0_ret, 6, "str_arg0_ret"); + ASSERT_EQ(skel->bss->str_arg1_ret, 16, "str_arg1_ret"); + ASSERT_EQ(skel->bss->args_match, 1, "args_match"); + ASSERT_EQ(skel->bss->str_args_match, 1, "str_args_match"); + +out: + copy_from_user_bprm__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/copy_from_user_bprm.c b/tools/testing/selftests/bpf/progs/copy_from_user_bprm.c new file mode 100644 index 000000000000..679363811edc --- /dev/null +++ b/tools/testing/selftests/bpf/progs/copy_from_user_bprm.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "vmlinux.h" + +#include +#include +#include +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +static const char expected_args[] = "first\0second-argument"; +static const char expected_arg0[] = "first"; +static const char expected_arg1[] = "second-argument"; + +int monitored_pid; +int bprm_argc; +int invalid_flags_ret; +int copy_ret; +int str_arg0_ret; +int str_arg1_ret; +int args_match; +int str_args_match; + +extern int bpf_copy_from_user_bprm(void *dst, u32 dst__sz, + const void *unsafe_ptr__ign, + const struct linux_binprm *bprm, + u64 flags) __ksym; + +extern int bpf_copy_from_user_bprm_str(void *dst, u32 dst__sz, + const void *unsafe_ptr__ign, + const struct linux_binprm *bprm, + u64 flags) __ksym; + +SEC("lsm.s/bprm_check_security") +int BPF_PROG(check_exec_args, struct linux_binprm *bprm, int ret) +{ + u32 pid = bpf_get_current_pid_tgid() >> 32; + char args[sizeof(expected_args)]; + char arg0[32]; + char arg1[32]; + + if (ret || pid != monitored_pid) + return ret; + + bprm_argc = bprm->argc; + + invalid_flags_ret = bpf_copy_from_user_bprm(args, sizeof(args), + (void *)bprm->p, bprm, 1); + + copy_ret = bpf_copy_from_user_bprm(args, sizeof(args), + (void *)bprm->p, bprm, 0); + if (copy_ret) + return 0; + + args_match = !__builtin_memcmp(args, expected_args, sizeof(expected_args)); + + str_arg0_ret = bpf_copy_from_user_bprm_str(arg0, sizeof(arg0), + (void *)bprm->p, bprm, + BPF_F_PAD_ZEROS); + if (str_arg0_ret != sizeof(expected_arg0)) + return 0; + + str_arg1_ret = bpf_copy_from_user_bprm_str(arg1, sizeof(arg1), + (void *)(bprm->p + str_arg0_ret), + bprm, BPF_F_PAD_ZEROS); + if (str_arg1_ret != sizeof(expected_arg1)) + return 0; + + str_args_match = !__builtin_memcmp(arg0, expected_arg0, sizeof(expected_arg0)) && + !__builtin_memcmp(arg1, expected_arg1, sizeof(expected_arg1)); + + return args_match && str_args_match ? -EPERM : 0; +} -- 2.55.0