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