From: Andrii Nakryiko <andriin@fb.com>
Date: Thu, 23 Apr 2020 22:20:44 -0700
Subject: bpf: Fix leak in LINK_UPDATE and enforce empty old_prog_fd
Patch-mainline: v5.7-rc3
Git-commit: 4adb7a4a151c65ac7e9c3a1aa462c84190d48385
References: bsc#1177028

Fix bug of not putting bpf_link in LINK_UPDATE command.
Also enforce zeroed old_prog_fd if no BPF_F_REPLACE flag is specified.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200424052045.4002963-1-andriin@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
 kernel/bpf/syscall.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3628,8 +3628,10 @@ static int link_update(union bpf_attr *a
 		return PTR_ERR(link);
 
 	new_prog = bpf_prog_get(attr->link_update.new_prog_fd);
-	if (IS_ERR(new_prog))
-		return PTR_ERR(new_prog);
+	if (IS_ERR(new_prog)) {
+		ret = PTR_ERR(new_prog);
+		goto out_put_link;
+	}
 
 	if (flags & BPF_F_REPLACE) {
 		old_prog = bpf_prog_get(attr->link_update.old_prog_fd);
@@ -3638,6 +3640,9 @@ static int link_update(union bpf_attr *a
 			old_prog = NULL;
 			goto out_put_progs;
 		}
+	} else if (attr->link_update.old_prog_fd) {
+		ret = -EINVAL;
+		goto out_put_progs;
 	}
 
 #ifdef CONFIG_CGROUP_BPF
@@ -3653,6 +3658,8 @@ out_put_progs:
 		bpf_prog_put(old_prog);
 	if (ret)
 		bpf_prog_put(new_prog);
+out_put_link:
+	bpf_link_put(link);
 	return ret;
 }