Improve bpf_map__reuse_fd() logic and ensure that dup'ed map FD is
"good" (>= 3) and has O_CLOEXEC flags. Use fcntl(F_DUPFD_CLOEXEC) for
that, similarly to ensure_good_fd() helper we already use in low-level
APIs that work with bpf() syscall.
Suggested-by: Lennart Poettering <lennart@xxxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 60ef4c5e3bee..47632606b06d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4414,18 +4414,17 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
if (!new_name)
return libbpf_err(-errno);
- new_fd = open("/", O_RDONLY | O_CLOEXEC);
+ /*
+ * Like dup(), but make sure new FD is >= 3 and has O_CLOEXEC set.
+ * This is similar to what we do in ensure_good_fd(), but without
+ * closing original FD.
+ */
+ new_fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
if (new_fd < 0) {
err = -errno;
goto err_free_new_name;
}
- new_fd = dup3(fd, new_fd, O_CLOEXEC);
- if (new_fd < 0) {
- err = -errno;
- goto err_close_new_fd;
- }
-
err = zclose(map->fd);
if (err) {
err = -errno;
--
2.34.1
