process-util: do not unblock unrelated signals while forking

This makes sure when we are blocking signals in preparation for fork()
we'll not temporarily unblock any signals previously set, by mistake.

It's safe for us to block more, but not to unblock signals already
blocked. Fix that.

Fixes: #35470

diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index 7a4d0b30e49f7065c957e8902e9dd7336fbe71c6..77045e6aa8e61390734c02fa91fb85b03dd9b690 100644 (file)
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -1402,11 +1402,6 @@ int must_be_root(void) {
         return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be root.");
 }
 
-static void restore_sigsetp(sigset_t **ssp) {
-        if (*ssp)
-                (void) sigprocmask(SIG_SETMASK, *ssp, NULL);
-}
-
 pid_t clone_with_nested_stack(int (*fn)(void *), int flags, void *userdata) {
         size_t ps;
         pid_t pid;
@@ -1446,6 +1441,11 @@ pid_t clone_with_nested_stack(int (*fn)(void *), int flags, void *userdata) {
         return pid;
 }
 
+static void restore_sigsetp(sigset_t **ssp) {
+        if (*ssp)
+                (void) sigprocmask(SIG_SETMASK, *ssp, NULL);
+}
+
 static int fork_flags_to_signal(ForkFlags flags) {
         return (flags & FORK_DEATHSIG_SIGTERM) ? SIGTERM :
                 (flags & FORK_DEATHSIG_SIGINT) ? SIGINT :
@@ -1498,8 +1498,8 @@ int safe_fork_full(
         }
 
         if (block_signals) {
-                if (sigprocmask(SIG_SETMASK, &ss, &saved_ss) < 0)
-                        return log_full_errno(prio, errno, "Failed to set signal mask: %m");
+                if (sigprocmask(SIG_BLOCK, &ss, &saved_ss) < 0)
+                        return log_full_errno(prio, errno, "Failed to block signal mask: %m");
                 saved_ssp = &saved_ss;
         }