sd-dameon: also sent ucred when our UID differs from EUID

Let's be explicit, and always send the messages from our UID and never
our EUID. Previously this behaviour was conditionalized only on whether
the PID was specified, which made this non-obvious.

(cherry picked from commit 9e1d021ee3f147486c5cfac69b3cbf6f4b36eb79)

Change-Id: I732ce2169e00f2f5fe8e7f7403d6f31dc66842a2

diff --git a/src/libsystemd/sd-daemon/sd-daemon.c b/src/libsystemd/sd-daemon/sd-daemon.c
index b20a7eb..b0ce9fc 100644 (file)
--- a/src/libsystemd/sd-daemon/sd-daemon.c
+++ b/src/libsystemd/sd-daemon/sd-daemon.c
@@ -416,7 +416,7 @@ _public_ int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char
         _cleanup_close_ int fd = -1;
         struct cmsghdr *cmsg = NULL;
         const char *e;
-        bool have_pid;
+        bool send_ucred;
         int r;
 
         if (!state) {
@@ -460,13 +460,16 @@ _public_ int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char
 
         msghdr.msg_namelen = SOCKADDR_UN_LEN(sockaddr.un);
 
-        have_pid = pid != 0 && pid != getpid();
+        send_ucred =
+                (pid != 0 && pid != getpid()) ||
+                getuid() != geteuid() ||
+                getgid() != getegid();
 
-        if (n_fds > 0 || have_pid) {
+        if (n_fds > 0 || send_ucred) {
                 /* CMSG_SPACE(0) may return value different than zero, which results in miscalculated controllen. */
                 msghdr.msg_controllen =
                         (n_fds > 0 ? CMSG_SPACE(sizeof(int) * n_fds) : 0) +
-                        (have_pid ? CMSG_SPACE(sizeof(struct ucred)) : 0);
+                        (send_ucred ? CMSG_SPACE(sizeof(struct ucred)) : 0);
 
                 msghdr.msg_control = alloca0(msghdr.msg_controllen);
 
@@ -478,11 +481,11 @@ _public_ int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char
 
                         memcpy(CMSG_DATA(cmsg), fds, sizeof(int) * n_fds);
 
-                        if (have_pid)
+                        if (send_ucred)
                                 assert_se(cmsg = CMSG_NXTHDR(&msghdr, cmsg));
                 }
 
-                if (have_pid) {
+                if (send_ucred) {
                         struct ucred *ucred;
 
                         cmsg->cmsg_level = SOL_SOCKET;
@@ -490,7 +493,7 @@ _public_ int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char
                         cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
 
                         ucred = (struct ucred*) CMSG_DATA(cmsg);
-                        ucred->pid = pid;
+                        ucred->pid = pid != 0 ? pid : getpid();
                         ucred->uid = getuid();
                         ucred->gid = getgid();
                 }
@@ -503,7 +506,7 @@ _public_ int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char
         }
 
         /* If that failed, try with our own ucred instead */
-        if (have_pid) {
+        if (send_ucred) {
                 msghdr.msg_controllen -= CMSG_SPACE(sizeof(struct ucred));
                 if (msghdr.msg_controllen == 0)
                         msghdr.msg_control = NULL;