lkml.org 
[lkml]   [2017]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] module: check if memory leak by module.
On Wed, 29 Mar 2017, Michal Hocko wrote:

> On Wed 29-03-17 11:32:02, Maninder Singh wrote:
> > This patch checks if any module which is going to be unloaded
> > is doing vmalloc memory leak or not.
>
> Hmm, how can you track _all_ vmalloc allocations done on behalf of the
> module? It is quite some time since I've checked kernel/module.c but
> from my vague understading your check is basically only about statically
> vmalloced areas by module loader. Is that correct? If yes then is this
> actually useful? Were there any bugs in the loader code recently? What
> led you to prepare this patch? All this should be part of the changelog!

Moreover, I don't understand one thing:

> > Logs:-
> > [ 129.336368] Module [test_module] is getting unloaded before doing vfree

ok, but...

> > +static void check_memory_leak(struct module *mod)
> > +{
> > + struct vmap_area *va;
> > +
> > + rcu_read_lock();
> > + list_for_each_entry_rcu(va, &vmap_area_list, list) {
> > + if (!(va->flags & VM_VM_AREA))
> > + continue;
> > + if ((mod->core_layout.base < va->vm->caller) &&
> > + (mod->core_layout.base + mod->core_layout.size) > va->vm->caller) {
> > + pr_err("Module [%s] is getting unloaded before doing vfree\n", mod->name);
> > + pr_err("Memory still allocated: addr:0x%lx - 0x%lx, pages %u\n",
> > + va->va_start, va->va_end, va->vm->nr_pages);
> > + pr_err("Allocating function %pS\n", va->vm->caller);
> > + }
> > +
> > + }
> > + rcu_read_unlock();
> > +}
> > +
> > /* Free a module, remove from lists, etc. */
> > static void free_module(struct module *mod)
> > {
> > + check_memory_leak(mod);
> > +

Of course, vfree() has not been called yet. It is the beginning of
free_module(). vfree() is one of the last things you need to do. See
module_memfree(). If I am not missing something, you get pr_err()
everytime a module is unloaded.

Regards,
Miroslav

\
 
 \ /
  Last update: 2017-03-29 10:09    [W:0.065 / U:0.512 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site