From: Cristian Rodríguez <cristian@rodriguez.im>
Date: Sun, 11 Feb 2024 18:53:30 +0000 (-0300)
Subject: Save and restore errno on signal handlers
X-Git-Tag: v2.42-start~536^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0754479d6a3d843cd96bfe8185b601f02d444300;p=thirdparty%2Futil-linux.git

Save and restore errno on signal handlers

"Fetching and setting the value of errno is async-signal-safe
provided that the signal handler saves errno on entry and
       restores its value before returning."

save and restore errno on cases where it is needed.
---

diff --git a/include/c.h b/include/c.h
index 61b95ab2dc..3b921ab33b 100644
--- a/include/c.h
+++ b/include/c.h
@@ -595,4 +595,13 @@ static inline void *reallocarray(void *ptr, size_t nmemb, size_t size)
 }
 #endif
 
+static inline void ul_reset_errno(int *saved_errno) {
+        if (*saved_errno < 0)
+                return;
+
+        errno = *saved_errno;
+}
+
+#define UL_PROTECT_ERRNO __attribute__((__cleanup__(ul_reset_errno))) \
+                         __attribute__((__unused__)) int __ul_saved_errno = errno
 #endif /* UTIL_LINUX_C_H */
diff --git a/lib/pager.c b/lib/pager.c
index 98814b5492..14bf071dbe 100644
--- a/lib/pager.c
+++ b/lib/pager.c
@@ -173,6 +173,7 @@ static void wait_for_pager(void)
 
 static void wait_for_pager_signal(int signo)
 {
+	UL_PROTECT_ERRNO;
 	wait_for_pager();
 	raise(signo);
 }
diff --git a/misc-utils/hardlink.c b/misc-utils/hardlink.c
index f9d3d09ac6..89046a9f75 100644
--- a/misc-utils/hardlink.c
+++ b/misc-utils/hardlink.c
@@ -1378,6 +1378,7 @@ static void to_be_called_atexit(void)
 */
 static void sighandler(int i)
 {
+	UL_PROTECT_ERRNO;
 	if (last_signal != SIGINT)
 		last_signal = i;
 	if (i == SIGINT)
diff --git a/text-utils/pg.c b/text-utils/pg.c
index 30ed04660b..8e01a9a5bd 100644
--- a/text-utils/pg.c
+++ b/text-utils/pg.c
@@ -371,6 +371,7 @@ static void skip(int direction)
 /* Signal handler while reading from input file. */
 static void sighandler(int signum)
 {
+	UL_PROTECT_ERRNO;
 	if (canjump && (signum == SIGINT || signum == SIGQUIT))
 		longjmp(jmpenv, signum);
 	tcsetattr(STDOUT_FILENO, TCSADRAIN, &otio);