fusermount: Close file descriptors with close_range() if possible

close_range() is much more efficient.

Also remove the lower limit of 3 and set it to 0, as 0 to 1
might have been closed by the application and might be valid.

1 files changed, 26 insertions, 1 deletions

diff --git a/util/fusermount.c b/util/fusermount.c
index b8437a0..8528342 100644
--- a/util/fusermount.c
+++ b/util/fusermount.c
@@ -1456,8 +1456,33 @@ static void show_version(void)
 static void close_inherited_fds(int cfd)
 {
 	int max_fd = sysconf(_SC_OPEN_MAX);
+	int rc;
 
-	for (int fd = 3; fd <= max_fd; fd++) {
+#ifdef CLOSE_RANGE_CLOEXEC
+	/* high range first to be able to log errors through stdout/err*/
+	rc = close_range(cfd + 1, ~0U, 0);
+	if (rc < 0) {
+		fprintf(stderr, "Failed to close high range of FDs: %s",
+			strerror(errno));
+		goto fallback;
+	}
+
+	rc = close_range(0, cfd - 1, 0);
+	if (rc < 0) {
+		fprintf(stderr, "Failed to close low range of FDs: %s",
+			strerror(errno));
+		goto fallback;
+	}
+#endif
+
+fallback:
+	/*
+	 * This also needs to close stdout/stderr, as the application
+	 * using libfuse might have closed these FDs and might be using
+	 * it. Although issue is now that logging errors won't be possible
+	 * after that.
+	 */
+	for (int fd = 0; fd <= max_fd; fd++) {
 		if (fd != cfd)
 			close(fd);
 	}