From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Fri, 13 Jun 2025 15:27:06 +0000 (+0900)
Subject: sd-dhcp-server: reopen fd only when it is valid
X-Git-Tag: v258-rc1~303^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=98b02dd7e73fc42676537dab885c70c45b0375fc;p=thirdparty%2Fsystemd.git

sd-dhcp-server: reopen fd only when it is valid

Fixes a bug in 11b88419ae0004547a0724aa459ddcb5d243f25c.
---

diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 099362d1ae3..335f01f1645 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -1605,9 +1605,13 @@ int sd_dhcp_server_set_lease_file(sd_dhcp_server *server, int dir_fd, const char
         if (!path_is_safe(path))
                 return -EINVAL;
 
-        _cleanup_close_ int fd = fd_reopen(dir_fd, O_CLOEXEC | O_DIRECTORY | O_PATH);
-        if (fd < 0)
-                return fd;
+        _cleanup_close_ int fd = AT_FDCWD; /* Unlike our usual coding style, AT_FDCWD needs to be set,
+                                            * to pass a 'valid' fd. */
+        if (dir_fd >= 0) {
+                fd = fd_reopen(dir_fd, O_CLOEXEC | O_DIRECTORY | O_PATH);
+                if (fd < 0)
+                        return fd;
+        }
 
         r = free_and_strdup(&server->lease_file, path);
         if (r < 0)