fix potential deadlock in dlerror buffer handling at thread exit

[musl] / src / process / fork.c

diff --git a/src/process/fork.c b/src/process/fork.c
index 012b7ca..ff71845 100644 (file)
--- a/src/process/fork.c
+++ b/src/process/fork.c
@@ -1,19 +1,84 @@
 #include <unistd.h>
-#include "syscall.h"
+#include <errno.h>
 #include "libc.h"
+#include "lock.h"
 #include "pthread_impl.h"
+#include "fork_impl.h"
+
+static volatile int *const dummy_lockptr = 0;
+
+weak_alias(dummy_lockptr, __at_quick_exit_lockptr);
+weak_alias(dummy_lockptr, __atexit_lockptr);
+weak_alias(dummy_lockptr, __gettext_lockptr);
+weak_alias(dummy_lockptr, __locale_lockptr);
+weak_alias(dummy_lockptr, __random_lockptr);
+weak_alias(dummy_lockptr, __sem_open_lockptr);
+weak_alias(dummy_lockptr, __stdio_ofl_lockptr);
+weak_alias(dummy_lockptr, __syslog_lockptr);
+weak_alias(dummy_lockptr, __timezone_lockptr);
+weak_alias(dummy_lockptr, __bump_lockptr);
+
+weak_alias(dummy_lockptr, __vmlock_lockptr);
+
+static volatile int *const *const atfork_locks[] = {
+       &__at_quick_exit_lockptr,
+       &__atexit_lockptr,
+       &__gettext_lockptr,
+       &__locale_lockptr,
+       &__random_lockptr,
+       &__sem_open_lockptr,
+       &__stdio_ofl_lockptr,
+       &__syslog_lockptr,
+       &__timezone_lockptr,
+       &__bump_lockptr,
+};
+
+static void dummy(int x) { }
+weak_alias(dummy, __fork_handler);
+weak_alias(dummy, __malloc_atfork);
+weak_alias(dummy, __ldso_atfork);
+
+static void dummy_0(void) { }
+weak_alias(dummy_0, __tl_lock);
+weak_alias(dummy_0, __tl_unlock);
 
 pid_t fork(void)
 {
-       pid_t ret;
-       if (libc.fork_handler) libc.fork_handler(-1);
-       ret = syscall(SYS_fork);
-       if (libc.lock && !ret) {
-               pthread_t self = __pthread_self();
-               self->pid = syscall(SYS_getpid);
-               self->tid = syscall(SYS_gettid);
-               libc.threads_minus_1 = 0;
+       sigset_t set;
+       __fork_handler(-1);
+       __block_app_sigs(&set);
+       int need_locks = libc.need_locks > 0;
+       if (need_locks) {
+               __ldso_atfork(-1);
+               __inhibit_ptc();
+               for (int i=0; i<sizeof atfork_locks/sizeof *atfork_locks; i++)
+                       if (*atfork_locks[i]) LOCK(*atfork_locks[i]);
+               __malloc_atfork(-1);
+               __tl_lock();
+       }
+       pthread_t self=__pthread_self(), next=self->next;
+       pid_t ret = _Fork();
+       int errno_save = errno;
+       if (need_locks) {
+               if (!ret) {
+                       for (pthread_t td=next; td!=self; td=td->next)
+                               td->tid = -1;
+                       if (__vmlock_lockptr) {
+                               __vmlock_lockptr[0] = 0;
+                               __vmlock_lockptr[1] = 0;
+                       }
+               }
+               __tl_unlock();
+               __malloc_atfork(!ret);
+               for (int i=0; i<sizeof atfork_locks/sizeof *atfork_locks; i++)
+                       if (*atfork_locks[i])
+                               if (ret) UNLOCK(*atfork_locks[i]);
+                               else **atfork_locks[i] = 0;
+               __release_ptc();
+               __ldso_atfork(!ret);
        }
-       if (libc.fork_handler) libc.fork_handler(!ret);
+       __restore_sigs(&set);
+       __fork_handler(!ret);
+       if (ret<0) errno = errno_save;
        return ret;
 }