fix race condition in pthread_kill

if thread id was reused by the kernel between the time pthread_kill
read it from the userspace pthread_t object and the time of the tgkill
syscall, a signal could be sent to the wrong thread. the tgkill
syscall was supposed to prevent this race (versus the old tkill
syscall) but it can't; it can only help in the case where the tid is
reused in a different process, but not when the tid is reused in the
same process.

the only solution i can see is an extra lock to prevent threads from
exiting while another thread is trying to pthread_kill them. it should
be very very cheap in the non-contended case.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
index 12f8ccfc..2089c857 100644
--- a/src/internal/pthread_impl.h
+++ b/src/internal/pthread_impl.h
@@ -46,6 +46,7 @@ struct pthread {
 	int unblock_cancel;
 	int delete_timer;
 	locale_t locale;
+	int killlock;
 };
 
 struct __timer {