From a3f1255f1891ddbaf3bb6a32af28569c0e6f3b91 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Thomas=20Wei=C3=9Fschuh?= <thomas@t-8ch.de>
Date: Tue, 7 May 2024 13:44:31 +0200
Subject: [PATCH] libuuid: clear uuidd cache on fork()
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After fork() the memory of the calling thread is preserved into the new
process. This also includes TLS.
Make sure to reset the cache after a fork to avoid reuse of cached
values.

Only the TLS of the thread calling fork() is relevant as that is the
only thread that gets forked.
New threads will received newly initialized TLS.

Fixes https://github.com/util-linux/util-linux/issues/3009
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---
 libuuid/src/Makemodule.am |  2 +-
 libuuid/src/gen_uuid.c    | 17 +++++++++++++++--
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/libuuid/src/Makemodule.am b/libuuid/src/Makemodule.am
index e58fa261cf..417fd2bd55 100644
--- a/libuuid/src/Makemodule.am
+++ b/libuuid/src/Makemodule.am
@@ -31,7 +31,7 @@ libuuid_la_SOURCES = \
 EXTRA_libuuid_la_DEPENDENCIES = \
 	libuuid/src/libuuid.sym
 
-libuuid_la_LIBADD       = $(LDADD) $(SOCKET_LIBS)
+libuuid_la_LIBADD       = $(LDADD) $(SOCKET_LIBS) -lpthread
 
 libuuid_la_CFLAGS = \
 	$(AM_CFLAGS) \
diff --git a/libuuid/src/gen_uuid.c b/libuuid/src/gen_uuid.c
index e82e005bef..9c690d5226 100644
--- a/libuuid/src/gen_uuid.c
+++ b/libuuid/src/gen_uuid.c
@@ -80,6 +80,8 @@
 #if defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)
 #include <sys/syscall.h>
 #endif
+#include <pthread.h>
+#include <signal.h>
 
 #include "all-io.h"
 #include "uuidP.h"
@@ -592,9 +594,21 @@ THREAD_LOCAL struct {
 	.cache_size = CS_MIN,
 };
 
+static void reset_uuidd_cache(void)
+{
+	memset(&uuidd_cache, 0, sizeof(uuidd_cache));
+	uuidd_cache.cache_size = CS_MIN;
+}
+
 static int uuid_generate_time_generic(uuid_t out) {
+	static volatile sig_atomic_t atfork_registered;
 	time_t	now;
 
+	if (!atfork_registered) {
+		pthread_atfork(NULL, NULL, reset_uuidd_cache);
+		atfork_registered = 1;
+	}
+
 	if (uuidd_cache.num > 0) { /* expire cache */
 		now = time(NULL);
 		if (now > uuidd_cache.last_time+1) {
@@ -623,8 +637,7 @@ static int uuid_generate_time_generic(uuid_t out) {
 			return 0;
 		}
 		/* request to daemon failed, reset cache */
-		uuidd_cache.num = 0;
-		uuidd_cache.cache_size = CS_MIN;
+		reset_uuidd_cache();
 	}
 	if (uuidd_cache.num > 0) { /* serve uuid from cache */
 		uuidd_cache.uu.time_low++;
-- 
2.47.2