release/5.2.33/libbpf-Fix-error-handling-in-bpf_map__reuse_fd.patch

From 96e54c1ac5b8cfc86511826c6827f718d7f9a043 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Sat, 2 Nov 2019 12:09:37 +0100
Subject: [PATCH] libbpf: Fix error handling in bpf_map__reuse_fd()
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commit d1b4574a4b86565325ef2e545eda8dfc9aa07c60 upstream.

bpf_map__reuse_fd() was calling close() in the error path before returning
an error value based on errno. However, close can change errno, so that can
lead to potentially misleading error messages. Instead, explicitly store
errno in the err variable before each goto.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/157269297769.394725.12634985106772698611.stgit@toke.dk
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0ccf6aa533ae..88d506951b07 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1503,16 +1503,22 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 		return -errno;
 
 	new_fd = open("/", O_RDONLY | O_CLOEXEC);
-	if (new_fd < 0)
+	if (new_fd < 0) {
+		err = -errno;
 		goto err_free_new_name;
+	}
 
 	new_fd = dup3(fd, new_fd, O_CLOEXEC);
-	if (new_fd < 0)
+	if (new_fd < 0) {
+		err = -errno;
 		goto err_close_new_fd;
+	}
 
 	err = zclose(map->fd);
-	if (err)
+	if (err) {
+		err = -errno;
 		goto err_close_new_fd;
+	}
 	free(map->name);
 
 	map->fd = new_fd;
@@ -1531,7 +1537,7 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 	close(new_fd);
 err_free_new_name:
 	free(new_name);
-	return -errno;
+	return err;
 }
 
 int bpf_map__resize(struct bpf_map *map, __u32 max_entries)
-- 
2.7.4