From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Thu, 13 Aug 2020 16:29:05 +0200
Subject: libbpf: Prevent overriding errno when logging errors
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Patch-mainline: v5.9-rc2
Git-commit: 23ab656be263813acc3c20623757d3cd1496d9e1
References: bsc#1177028

Turns out there were a few more instances where libbpf didn't save the
errno before writing an error message, causing errno to be overridden by
the printf() return and the error disappearing if logging is enabled.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200813142905.160381-1-toke@redhat.com
Acked-by: Gary Lin <glin@suse.com>
---
 tools/lib/bpf/libbpf.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3477,10 +3477,11 @@ bpf_object__probe_global_data(struct bpf
 
 	map = bpf_create_map_xattr(&map_attr);
 	if (map < 0) {
-		cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+		ret = -errno;
+		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
 		pr_warning("Error in %s():%s(%d). Couldn't create simple array map.\n",
-			   __func__, cp, errno);
-		return -errno;
+			   __func__, cp, -ret);
+		return ret;
 	}
 
 	insns[0].imm = map;
@@ -6014,9 +6015,10 @@ int bpf_program__pin_instance(struct bpf
 	}
 
 	if (bpf_obj_pin(prog->instances.fds[instance], path)) {
-		cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+		err = -errno;
+		cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
 		pr_warning("failed to pin program: %s\n", cp);
-		return -errno;
+		return err;
 	}
 	pr_debug("pinned program '%s'\n", path);