protect destruction of process-shared mutexes against robust list races

[musl] / src / thread / pthread_mutexattr_setrobust.c

diff --git a/src/thread/pthread_mutexattr_setrobust.c b/src/thread/pthread_mutexattr_setrobust.c
index 4a296ba..30a9ac3 100644 (file)
--- a/src/thread/pthread_mutexattr_setrobust.c
+++ b/src/thread/pthread_mutexattr_setrobust.c
@@ -1,9 +1,23 @@
 #include "pthread_impl.h"
+#include "syscall.h"
+
+static volatile int check_robust_result = -1;
 
 int pthread_mutexattr_setrobust(pthread_mutexattr_t *a, int robust)
 {
        if (robust > 1U) return EINVAL;
-       *a &= ~4;
-       *a |= robust*4;
+       if (robust) {
+               int r = check_robust_result;
+               if (r < 0) {
+                       void *p;
+                       size_t l;
+                       r = -__syscall(SYS_get_robust_list, 0, &p, &l);
+                       a_store(&check_robust_result, r);
+               }
+               if (r) return r;
+               a->__attr |= 4;
+               return 0;
+       }
+       a->__attr &= ~4;
        return 0;
 }