From 051b36e399db12d41cb6696c88722fce6231d5ec Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Mon, 27 Sep 2021 20:29:39 +0530
Subject: [PATCH] libbpf: Fix skel_internal.h to set errno on loader retval < 0
Git-commit: e68ac0082787f4e8ee6ae5b19076ec7709ce715b
Patch-mainline: v5.16-rc1
References: stable-5.14.19
[ Upstream commit e68ac0082787f4e8ee6ae5b19076ec7709ce715b ]
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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210927145941.1383001-11-memxor@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
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;
--
2.26.2