From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: "Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
netdev@vger.kernel.org
Subject: [PATCH bpf-next v5 10/12] libbpf: Fix skel_internal.h to set errno on loader retval < 0
Date: Mon, 27 Sep 2021 20:29:39 +0530 [thread overview]
Message-ID: <20210927145941.1383001-11-memxor@gmail.com> (raw)
In-Reply-To: <20210927145941.1383001-1-memxor@gmail.com>
When the loader indicates an internal error (result of a checked bpf
system call), it returns the result in attr.test.retval. However, tests
that rely on ASSERT_OK_PTR on NULL (returned from light skeleton) may
miss that NULL denotes an error if errno is set to 0. This would result
in skel pointer being NULL, while ASSERT_OK_PTR returning 1, leading to
a SEGV on dereference of skel, because libbpf_get_error relies on the
assumption that errno is always set in case of error for ptr == NULL.
In particular, this was observed for the ksyms_module test. When
executed using `./test_progs -t ksyms`, prior tests manipulated errno
and the test didn't crash when it failed at ksyms_module load, while
using `./test_progs -t ksyms_module` crashed due to errno being
untouched.
Fixes: 67234743736a (libbpf: Generate loader program out of BPF ELF file.)
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
tools/lib/bpf/skel_internal.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index b22b50c1b173..9cf66702fa8d 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -105,10 +105,12 @@ static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts)
err = skel_sys_bpf(BPF_PROG_RUN, &attr, sizeof(attr));
if (err < 0 || (int)attr.test.retval < 0) {
opts->errstr = "failed to execute loader prog";
- if (err < 0)
+ if (err < 0) {
err = -errno;
- else
+ } else {
err = (int)attr.test.retval;
+ errno = -err;
+ }
goto out;
}
err = 0;
--
2.33.0
next prev parent reply other threads:[~2021-09-27 15:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 14:59 [PATCH bpf-next v5 00/12] Support kernel module function calls from eBPF Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 01/12] bpf: Introduce BPF support for kernel module function calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 02/12] bpf: Be conservative while processing invalid kfunc calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 03/12] bpf: btf: Introduce helpers for dynamic BTF set registration Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 04/12] tools: Allow specifying base BTF file in resolve_btfids Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 05/12] bpf: Enable TCP congestion control kfunc from modules Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 06/12] libbpf: Support kernel module function calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 07/12] libbpf: Resolve invalid weak kfunc calls with imm = 0, off = 0 Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 08/12] libbpf: Make gen_loader data aligned Kumar Kartikeya Dwivedi
2021-09-29 20:50 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 09/12] libbpf: Update gen_loader to emit BTF_KIND_FUNC relocations Kumar Kartikeya Dwivedi
2021-09-29 0:01 ` Alexei Starovoitov
2021-09-29 0:10 ` Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` Kumar Kartikeya Dwivedi [this message]
2021-09-30 3:45 ` [PATCH bpf-next v5 10/12] libbpf: Fix skel_internal.h to set errno on loader retval < 0 Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 11/12] bpf: selftests: Fix fd cleanup in get_branch_snapshot Kumar Kartikeya Dwivedi
2021-09-28 23:58 ` Song Liu
2021-09-29 20:26 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 12/12] bpf: selftests: Add selftests for module kfunc support Kumar Kartikeya Dwivedi
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