libbpf: don't close(-1) in multi-uprobe feature detector

commit 7d0b395 upstream.

Guard close(link_fd) with extra link_fd >= 0 check to prevent close(-1).

Detected by Coverity static analysis.

Fixes: 04d939a ("libbpf: detect broken PID filtering logic for multi-uprobe")
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: anakryiko

tools/lib/bpf/features.c

@@ -393,7 +393,8 @@ static int probe_uprobe_multi_link(int token_fd)
 	err = -errno; /* close() can clobber errno */
 
 	if (link_fd >= 0 || err != -EBADF) {
-		close(link_fd);
+		if (link_fd >= 0)
+			close(link_fd);
 		close(prog_fd);
 		return 0;
 	}