[PATCH userspace v2 3/6] libselinux: make selinux_log() thread-safe

[Ondrej Mosnacek <omosnace@xxxxxxxxxx>]

Ensure that selinux_log() is thread-safe by guarding the call to the
underlying callback with a mutex.

Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
 libselinux/src/callbacks.c |  8 +++++---
 libselinux/src/callbacks.h | 13 ++++++++++++-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/libselinux/src/callbacks.c b/libselinux/src/callbacks.c
index c18ccc54..469c4055 100644
--- a/libselinux/src/callbacks.c
+++ b/libselinux/src/callbacks.c
@@ -10,6 +10,8 @@
 #include <selinux/selinux.h>
 #include "callbacks.h"
 
+pthread_mutex_t log_mutex = PTHREAD_MUTEX_INITIALIZER;
+
 /* default implementations */
 static int __attribute__ ((format(printf, 2, 3)))
 default_selinux_log(int type __attribute__((unused)), const char *fmt, ...)
@@ -56,7 +58,7 @@ default_selinux_policyload(int seqno __attribute__((unused)))
 
 /* callback pointers */
 int __attribute__ ((format(printf, 2, 3)))
-(*selinux_log)(int, const char *, ...) =
+(*selinux_log_direct)(int, const char *, ...) =
 	default_selinux_log;
 
 int
@@ -81,7 +83,7 @@ selinux_set_callback(int type, union selinux_callback cb)
 {
 	switch (type) {
 	case SELINUX_CB_LOG:
-		selinux_log = cb.func_log;
+		selinux_log_direct = cb.func_log;
 		break;
 	case SELINUX_CB_AUDIT:
 		selinux_audit = cb.func_audit;
@@ -106,7 +108,7 @@ selinux_get_callback(int type)
 
 	switch (type) {
 	case SELINUX_CB_LOG:
-		cb.func_log = selinux_log;
+		cb.func_log = selinux_log_direct;
 		break;
 	case SELINUX_CB_AUDIT:
 		cb.func_audit = selinux_audit;
diff --git a/libselinux/src/callbacks.h b/libselinux/src/callbacks.h
index 03d87f0c..f4dab157 100644
--- a/libselinux/src/callbacks.h
+++ b/libselinux/src/callbacks.h
@@ -10,9 +10,11 @@
 #include <string.h>
 #include <selinux/selinux.h>
 
+#include "selinux_internal.h"
+
 /* callback pointers */
 extern int __attribute__ ((format(printf, 2, 3)))
-(*selinux_log) (int type, const char *, ...) ;
+(*selinux_log_direct) (int type, const char *, ...) ;
 
 extern int
 (*selinux_audit) (void *, security_class_t, char *, size_t) ;
@@ -26,4 +28,13 @@ extern int
 extern int
 (*selinux_netlink_policyload) (int seqno) ;
 
+/* Thread-safe selinux_log() function */
+extern pthread_mutex_t log_mutex;
+
+#define selinux_log(type, ...) do { \
+	__pthread_mutex_lock(&log_mutex); \
+	selinux_log_direct(type, __VA_ARGS__); \
+	__pthread_mutex_unlock(&log_mutex); \
+} while(0)
+
 #endif				/* _SELINUX_CALLBACKS_H_ */
-- 
2.31.1