From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Mon, 23 Feb 2026 18:51:25 +0000 (+0100)
Subject: lib/pager: Use async-signal safe signal handler
X-Git-Tag: v2.43-devel~48^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=89588ac31e48d25292406b932b6479f12e30bf42;p=thirdparty%2Futil-linux.git

lib/pager: Use async-signal safe signal handler

Accessing pager_process.pid from within a signal handler is, by strict C
language interpretation, not signal safe.

Wait for all children (and thus for pager_process.pid as well) instead.
The current users dmesg and fdisk have no further children so this is a
good compromise here.

The signal handler is used for SIGINT, SIGHUP, SIGTERM, SIGQUIT. From a
terminal perspective, these are normally intercepted by the child, not
the parent.

Since wait_for_pager is never reached by a signal handler anymore, a
regular err() call is now possible. Just make sure that no exit function
handler could ever loop endlessly.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
---

diff --git a/lib/pager.c b/lib/pager.c
index 3dc213dc9..b6321d2b0 100644
--- a/lib/pager.c
+++ b/lib/pager.c
@@ -109,9 +109,12 @@ static int wait_for_pager(void)
 
 	do {
 		waiting = waitpid(pager_process.pid, &status, 0);
-		if (waiting == -1 && errno != EINTR)
-			ul_sig_err(EXIT_FAILURE, "waitpid failed");
-	} while (waiting == -1);
+	} while (waiting == -1 && errno == EINTR);
+
+	pager_process.pid = 0;
+
+	if (waiting == -1)
+		err(EXIT_FAILURE, "waitpid failed");
 
 	if (waiting == pager_process.pid && WIFEXITED(status))
 		return WEXITSTATUS(status);
@@ -137,7 +140,10 @@ static void wait_for_pager_signal(int signo __attribute__ ((__unused__)))
 	close(STDOUT_FILENO);
 	close(STDERR_FILENO);
 
-	wait_for_pager();
+	/* async-signal safe: wait for all children, including pager */
+	while (wait(NULL) != -1 || errno == EINTR)
+		;
+
 	_exit(EXIT_FAILURE);
 }