libbpf: Prevent overriding errno when logging errors

[ Upstream commit 23ab656be263813acc3c20623757d3cd1496d9e1 ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e7642a6e39f9e4e2ce7076e41308afd005780984..e0b88f0013b74e70314ce05287186381511694bf 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3319,10 +3319,11 @@ bpf_object__probe_global_data(struct bpf_object *obj)
 
        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_warn("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;
@@ -5779,9 +5780,10 @@ int bpf_program__pin_instance(struct bpf_program *prog, const char *path,
        }
 
        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_warn("failed to pin program: %s\n", cp);
-               return -errno;
+               return err;
        }
        pr_debug("pinned program '%s'\n", path);