https://gitlab.com/NTPsec/ntpsec/-/commit/a49d53b7fe1d
https://bugs.gentoo.org/851531

From: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Date: Sat, 11 Jun 2022 15:16:15 +0200
Subject: [PATCH] ntpd/ntp_sandbox.c: allow readv() for glibc nscd
 getaddrinfo() provider

Otherwise, ntpd crashes from time to time with the following stack trace:
#0  0x00007f5763bfac4d in readv () from /lib64/libc.so.6
#1  0x00007f5763c48b4c in __readvall () from /lib64/libc.so.6
#2  0x00007f5763c467ed in nscd_gethst_r () from /lib64/libc.so.6
#3  0x00007f5763c46c0d in __nscd_gethostbyname2_r () from /lib64/libc.so.6
#4  0x00007f5763c15a2a in gethostbyname2_r () from /lib64/libc.so.6
#5  0x00007f5763bed3ca in gaih_inet.constprop () from /lib64/libc.so.6
#6  0x00007f5763bee225 in getaddrinfo () from /lib64/libc.so.6
#7  0x000055fcf0ad6544 in open_TCP_socket ()
#8  0x000055fcf0ad79b4 in nts_probe ()
#9  0x000055fcf0ac37c4 in dns_lookup ()
#10 0x00007f5763b8205a in start_thread () from /lib64/libc.so.6
#11 0x00007f5763c05d1c in clone3 () from /lib64/libc.so.6

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
--- a/ntpd/ntp_sandbox.c
+++ b/ntpd/ntp_sandbox.c
@@ -357,6 +357,7 @@ int scmp_sc[] = {
 	SCMP_SYS(poll),
 	SCMP_SYS(pselect6),
 	SCMP_SYS(read),
+	SCMP_SYS(readv),	/* nscd getaddrinfo() provider */
 	SCMP_SYS(recvfrom),    /* Comment this out for testing.
 				* It will die on the first reply.
 				* (Or maybe sooner if a request arrives.)
GitLab