fix missing synchronization of fork with abort

if the multithreaded parent forked while another thread was calling
sigaction for SIGABRT or calling abort, the child could inherit a lock
state in which future calls to abort will deadlock, or in which the
disposition for SIGABRT has already been reset to SIG_DFL. this is
nonconforming since abort is AS-safe and permitted to be called
concurrently with fork or in the MT-forked child.

diff --git a/src/process/fork.c b/src/process/fork.c
index dbaa940..17fb87a 100644 (file)
--- a/src/process/fork.c
+++ b/src/process/fork.c
@@ -3,6 +3,7 @@
 #include <signal.h>
 #include "syscall.h"
 #include "libc.h"
+#include "lock.h"
 #include "pthread_impl.h"
 
 static void dummy(int x)
@@ -19,6 +20,7 @@ pid_t fork(void)
        __fork_handler(-1);
        __block_all_sigs(&set);
        __aio_atfork(-1);
+       LOCK(__abort_lock);
 #ifdef SYS_fork
        ret = __syscall(SYS_fork);
 #else
@@ -34,6 +36,7 @@ pid_t fork(void)
                libc.threads_minus_1 = 0;
                if (libc.need_locks) libc.need_locks = -1;
        }
+       UNLOCK(__abort_lock);
        __aio_atfork(!ret);
        __restore_sigs(&set);
        __fork_handler(!ret);