core: use fexecve() to spawn children

We base the smack/selinux setup on the executable. Let's open the file
once and use the same fd for that setup and the subsequent execve.

diff --git a/src/core/execute.c b/src/core/execute.c
index bdd6857fe103a04ffdffdc3de887a551dd1f04d7..f1d6f87755e8af379766a21baf60249b200f53e0 100644 (file)
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -2881,11 +2881,11 @@ static int setup_credentials(
 #if ENABLE_SMACK
 static int setup_smack(
                 const ExecContext *context,
-                const char *executable) {
+                int executable_fd) {
         int r;
 
         assert(context);
-        assert(executable);
+        assert(executable_fd >= 0);
 
         if (context->smack_process_label) {
                 r = mac_smack_apply_pid(0, context->smack_process_label);
@@ -2896,7 +2896,7 @@ static int setup_smack(
         else {
                 _cleanup_free_ char *exec_label = NULL;
 
-                r = mac_smack_read(executable, SMACK_ATTR_EXEC, &exec_label);
+                r = mac_smack_read_fd(executable_fd, SMACK_ATTR_EXEC, &exec_label);
                 if (r < 0 && !IN_SET(r, -ENODATA, -EOPNOTSUPP))
                         return r;
 
@@ -3717,7 +3717,7 @@ static int exec_child(
         /* In case anything used libc syslog(), close this here, too */
         closelog();
 
-        int keep_fds[n_fds + 1];
+        int keep_fds[n_fds + 2];
         memcpy_safe(keep_fds, fds, n_fds * sizeof(int));
         n_keep_fds = n_fds;
 
@@ -4230,7 +4230,8 @@ static int exec_child(
          * shall execute. */
 
         _cleanup_free_ char *executable = NULL;
-        r = find_executable_full(command->path, false, &executable, NULL);
+        _cleanup_close_ int executable_fd = -1;
+        r = find_executable_full(command->path, false, &executable, &executable_fd);
         if (r < 0) {
                 if (r != -ENOMEM && (command->flags & EXEC_COMMAND_IGNORE_FAILURE)) {
                         log_struct_errno(LOG_INFO, r,
@@ -4253,6 +4254,12 @@ static int exec_child(
                                         "EXECUTABLE=%s", command->path);
         }
 
+        r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, executable_fd, &executable_fd);
+        if (r < 0) {
+                *exit_status = EXIT_FDS;
+                return log_unit_error_errno(unit, r, "Failed to shift fd and set FD_CLOEXEC: %m");
+        }
+
 #if HAVE_SELINUX
         if (needs_sandboxing && use_selinux && params->selinux_context_net && socket_fd >= 0) {
                 r = mac_selinux_get_child_mls_label(socket_fd, executable, context->selinux_context, &mac_selinux_context_net);
@@ -4301,7 +4308,7 @@ static int exec_child(
                 /* LSM Smack needs the capability CAP_MAC_ADMIN to change the current execution security context of the
                  * process. This is the latest place before dropping capabilities. Other MAC context are set later. */
                 if (use_smack) {
-                        r = setup_smack(context, executable);
+                        r = setup_smack(context, executable_fd);
                         if (r < 0) {
                                 *exit_status = EXIT_SMACK_PROCESS_LABEL;
                                 return log_unit_error_errno(unit, r, "Failed to set SMACK process label: %m");
@@ -4571,7 +4578,7 @@ static int exec_child(
                 }
         }
 
-        execve(executable, final_argv, accum_env);
+        fexecve(executable_fd, final_argv, accum_env);
         r = -errno;
 
         if (exec_fd >= 0) {

diff --git a/src/shared/exec-util.c b/src/shared/exec-util.c
index 8fb936dcce45ac3effd6f7cadd13040a15410c11..a93c206d9a3791c281658ca893f944ad6d35bf1d 100644 (file)
--- a/src/shared/exec-util.c
+++ b/src/shared/exec-util.c
@@ -33,7 +33,6 @@
 assert_cc(EAGAIN == EWOULDBLOCK);
 
 static int do_spawn(const char *path, char *argv[], int stdout_fd, pid_t *pid) {
-
         pid_t _pid;
         int r;