[PATCH bpf-next] libbpf: fix bpf_object name determination for bpf_object__open_file()

If bpf_object__open_file() gets path like "some/dir/obj.o", it should derive
BPF object's name as "obj" (unless overriden through opts->object_name).
Instead, due to using `path` as a fallback value for opts->obj_name, path is
used as is for object name, so for above example BPF object's name will be
verbatim "some/dir/obj", which leads to all sorts of troubles, especially when
internal maps are concern (they are using up to 8 characters of object name).
Fix that by ensuring object_name stays NULL, unless overriden.

Fixes: 291ee02b5e40 ("libbpf: Refactor bpf_object__open APIs to use common opts")
Signed-off-by: Andrii Nakryiko <redacted>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a4e250a369c6..e1698461c6b3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -3940,7 +3940,7 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
 	if (!OPTS_VALID(opts, bpf_object_open_opts))
 		return ERR_PTR(-EINVAL);
 
-	obj_name = OPTS_GET(opts, object_name, path);
+	obj_name = OPTS_GET(opts, object_name, NULL);
 	if (obj_buf) {
 		if (!obj_name) {
 			snprintf(tmp_name, sizeof(tmp_name), "%lx-%lx",

-- 
2.17.1

On Thu, Nov 21, 2019 at 4:36 PM Andrii Nakryiko [off-list ref] wrote:

If bpf_object__open_file() gets path like "some/dir/obj.o", it should derive
BPF object's name as "obj" (unless overriden through opts->object_name).
Instead, due to using `path` as a fallback value for opts->obj_name, path is
used as is for object name, so for above example BPF object's name will be
verbatim "some/dir/obj", which leads to all sorts of troubles, especially when
internal maps are concern (they are using up to 8 characters of object name).
Fix that by ensuring object_name stays NULL, unless overriden.

Fixes: 291ee02b5e40 ("libbpf: Refactor bpf_object__open APIs to use common opts")
Signed-off-by: Andrii Nakryiko <redacted>

Applied to bpf-next. Thanks