log: never log into foreign fd #2 in PID 1 or its pre-execve() children

Fixes: #5401

diff --git a/src/basic/log.c b/src/basic/log.c
index e6d2d61d72b8946121a2a66324fe5709c2522775..36efc9ac7d8eaf598f776ba831c605d0f78f8070 100644 (file)
--- a/src/basic/log.c
+++ b/src/basic/log.c
@@ -72,6 +72,7 @@ static bool show_color = false;
 static bool show_location = false;
 
 static bool upgrade_syslog_to_journal = false;
+static bool always_reopen_console = false;
 
 /* Akin to glibc's __abort_msg; which is private and we hence cannot
  * use here. */
@@ -95,7 +96,7 @@ static int log_open_console(void) {
         if (console_fd >= 0)
                 return 0;
 
-        if (getpid() == 1) {
+        if (always_reopen_console) {
                 console_fd = open_terminal("/dev/console", O_WRONLY|O_NOCTTY|O_CLOEXEC);
                 if (console_fd < 0)
                         return console_fd;
@@ -1171,3 +1172,7 @@ int log_syntax_internal(
                         unit_fmt, unit,
                         NULL);
 }
+
+void log_set_always_reopen_console(bool b) {
+        always_reopen_console = b;
+}

diff --git a/src/basic/log.h b/src/basic/log.h
index 9cacbb6b70f58f9d57b829537eb5436ea2d96a55..72714e02e5625992241e271537dd9041af0c909a 100644 (file)
--- a/src/basic/log.h
+++ b/src/basic/log.h
@@ -220,6 +220,7 @@ LogTarget log_target_from_string(const char *s) _pure_;
 void log_received_signal(int level, const struct signalfd_siginfo *si);
 
 void log_set_upgrade_syslog_to_journal(bool b);
+void log_set_always_reopen_console(bool b);
 
 int log_syntax_internal(
                 const char *unit,

diff --git a/src/core/main.c b/src/core/main.c
index 3c6b18229c841d637b6473a49acc7b598b2335da..bcf9ea5f25a07379d1aad01d4be821848b17e126 100644 (file)
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1414,10 +1414,17 @@ int main(int argc, char *argv[]) {
 
         log_set_upgrade_syslog_to_journal(true);
 
-        /* Disable the umask logic */
-        if (getpid() == 1)
+        if (getpid() == 1) {
+                /* Disable the umask logic */
                 umask(0);
 
+                /* Always reopen /dev/console when running as PID 1 or one of its pre-execve() children. This is
+                 * important so that we never end up logging to any foreign stderr, for example if we have to log in a
+                 * child process right before execve()'ing the actual binary, at a point in time where socket
+                 * activation stderr/stdout area already set up. */
+                log_set_always_reopen_console(true);
+        }
+
         if (getpid() == 1 && detect_container() <= 0) {
 
                 /* Running outside of a container as PID 1 */