Re: module: s390: keep mod_arch_specific for livepatch modules

+++ Miroslav Benes [16/12/15 13:02 +0100]:

On Mon, 30 Nov 2015, Jessica Yu wrote:

quoted

Livepatch needs to utilize the symbol information contained in the
mod_arch_specific struct in order to be able to call the s390
apply_relocate_add() function to apply relocations. Remove the redundant
vfree() in module_finalize() since module_arch_freeing_init() (which also frees
said structures) is called in do_init_module(). Keep a reference to syminfo if
the module is a livepatch module and free the structures in
module_arch_cleanup(). If the module isn't a livepatch module, we free the
structures in module_arch_freeing_init() as usual.

Signed-off-by: Jessica Yu <redacted>
---
 arch/s390/kernel/module.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index 0c1a679..17a1979 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c

@@ -51,6 +51,9 @@ void *module_alloc(unsigned long size)

 void module_arch_freeing_init(struct module *mod)
 {
+	if (mod->klp)
+		return;
+
 	vfree(mod->arch.syminfo);
 	mod->arch.syminfo = NULL;
 }

Hm, this is problematic. module_arch_freeing_init() is called from
module_deallocate() and this is called in the error path in load_module().
So if there was an error during load_module() of livepatch module which
led to free_modinfo label or behind mod->arch.syminfo would not be freed
at all. module_arch_cleanup() is called earlier under
free_arch_cleanup.

Gah. Good catch. How about we add an additional check to see if
mod->state is MODULE_STATE_LIVE? If so, we can return. This means
we're coming from do_init_module(). If module_arch_freeing_init() was
called and the module was in a state other than MODULE_STATE_LIVE
(UNFORMED, GOING, COMING), we know we need to free. Think that would
work?

Jessica