core: do not reset tty if there's no tty configured

Otherwise a lock is taken, which can be taken by multiple units at the
same time, depending on each other, causing a deadlock.

Fixes https://github.com/systemd/systemd/issues/29682

diff --git a/src/core/execute.c b/src/core/execute.c
index da416842cea8cc9955cb689fda267a0ef48afbce..35baac32249362aa4916c0ed3161698a89f6ac13 100644 (file)
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -73,6 +73,20 @@
 #include "user-util.h"
 #include "utmp-wtmp.h"
 
+static bool is_terminal_input(ExecInput i) {
+        return IN_SET(i,
+                      EXEC_INPUT_TTY,
+                      EXEC_INPUT_TTY_FORCE,
+                      EXEC_INPUT_TTY_FAIL);
+}
+
+static bool is_terminal_output(ExecOutput o) {
+        return IN_SET(o,
+                      EXEC_OUTPUT_TTY,
+                      EXEC_OUTPUT_KMSG_AND_CONSOLE,
+                      EXEC_OUTPUT_JOURNAL_AND_CONSOLE);
+}
+
 const char *exec_context_tty_path(const ExecContext *context) {
         assert(context);
 
@@ -114,9 +128,10 @@ void exec_context_tty_reset(const ExecContext *context, const ExecParameters *p)
 
         const char *path = exec_context_tty_path(context);
 
-        if (p && p->stdin_fd >= 0)
+        if (p && p->stdin_fd >= 0 && isatty(p->stdin_fd))
                 fd = p->stdin_fd;
-        else if (path) {
+        else if (path && (context->tty_path || is_terminal_input(context->std_input) ||
+                        is_terminal_output(context->std_output) || is_terminal_output(context->std_error))) {
                 fd = _fd = open_terminal(path, O_RDWR|O_NOCTTY|O_CLOEXEC|O_NONBLOCK);
                 if (fd < 0)
                         return (void) log_debug_errno(fd, "Failed to open terminal '%s', ignoring: %m", path);
@@ -148,20 +163,6 @@ void exec_context_tty_reset(const ExecContext *context, const ExecParameters *p)
                 (void) vt_disallocate(path);
 }
 
-static bool is_terminal_input(ExecInput i) {
-        return IN_SET(i,
-                      EXEC_INPUT_TTY,
-                      EXEC_INPUT_TTY_FORCE,
-                      EXEC_INPUT_TTY_FAIL);
-}
-
-static bool is_terminal_output(ExecOutput o) {
-        return IN_SET(o,
-                      EXEC_OUTPUT_TTY,
-                      EXEC_OUTPUT_KMSG_AND_CONSOLE,
-                      EXEC_OUTPUT_JOURNAL_AND_CONSOLE);
-}
-
 bool exec_needs_network_namespace(const ExecContext *context) {
         assert(context);