libffi prevents p11-kit from being usable with selinux

Nikos Mavrogiannopoulos nmav at
Mon Sep 21 03:22:49 PDT 2015

 I am debugging an issue when using p11-kit with apache which is due to
libffi. I'll explain the issue below, and have some questions even more

Once I start apache in Fedora with mod_gnutls using a PKCS #11 HSM I

(p11-kit:11686) p11_kit_module_load: in:
(p11-kit:11686) load_module_from_file_inlock: module path is relative,
loading from: /usr/lib64/pkcs11
(p11-kit:11686) load_module_from_file_inlock: loading module from path:
(p11-kit:11686) dlopen_and_get_function_list: opened module:
ffi_closure_alloc failed
p11-kit: shouldn't be reached at init_wrapper_funcs
p11-kit: shouldn't be reached at p11_virtual_wrap
p11-kit: '*module != NULL' not true at prepare_module_inlock_reentrant
(p11-kit:11686) p11_kit_module_load: out: fail

That issue is not there when SELinux is set to not enforcing. The
SELinux warning is:

"SELinux is preventing /usr/sbin/httpd from execute access on the file
/tmp/ffisox7RN (deleted)."

That is, libffi's temp file which is used to mmap memory for execution
is blocked by SELinux's policy. I find the policy of blocking execution
in tmp quite reasonable, so I think that libffi is to blame here.

The question is, (1) why does p11-kit need the libffi closure for that
module? I believe that should have been needed only when using the
proxy module, is that correct? (btw. having a high level description of
 p11-kit operation would be really helpful)

If we cannot avoid the closure, any good ideas on how could libffi get
memory to execute without using /tmp?


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