[PATCH bpf-next] libbpf: fix errno is overwritten after being closed.

[Xin Liu]

In the ensure_good_fd function, if the fcntl function succeeds but
the close function fails, ensure_good_fd returns a normal fd and
sets errno, which may cause users to misunderstand. The close
failure is not a serious problem, and the correct FD has been
handed over to the upper-layer application. Let's restore errno here.

Signed-off-by: Xin Liu <liuxin350@xxxxxxxxxx>
---
 tools/lib/bpf/libbpf_internal.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 377642ff51fc..98333a6c38e9 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -543,10 +543,9 @@ static inline int ensure_good_fd(int fd)
 		fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
 		saved_errno = errno;
 		close(old_fd);
-		if (fd < 0) {
+		errno = saved_errno;
+		if (fd < 0)
 			pr_warn("failed to dup FD %d to FD > 2: %d\n", old_fd, -saved_errno);
-			errno = saved_errno;
-		}
 	}
 	return fd;
 }
-- 
2.33.0