commit 217a74a85cdd60df236c296ad88142b78d35eccf

Author: Andreas Schwab <schwab@suse.de>

Date:   Mon Dec 8 15:13:38 2014 +0100

    Don't touch user-controlled stdio locks in forked child (bug 12847)

    The stdio locks for streams with the _IO_USER_LOCK flag should not be

    touched by internal code.

--- glibc-2.17-c758a686/nptl/sysdeps/unix/sysv/linux/fork.c

+++ glibc-2.17-c758a686/nptl/sysdeps/unix/sysv/linux/fork.c

@@ -45,7 +45,8 @@

   _IO_ITER i;

   for (i = _IO_iter_begin(); i != _IO_iter_end(); i = _IO_iter_next(i))

-    _IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));

+    if ((_IO_iter_file (i)->_flags & _IO_USER_LOCK) == 0)

+      _IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));

 }