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Date: Wed, 29 Mar 2017 10:02:24 +0200 (CEST) From: Miroslav Benes <mbenes@...e.cz> To: Michal Hocko <mhocko@...nel.org> cc: Maninder Singh <maninder1.s@...sung.com>, jeyu@...hat.com, rusty@...tcorp.com.au, akpm@...ux-foundation.org, chris@...is-wilson.co.uk, aryabinin@...tuozzo.com, joonas.lahtinen@...ux.intel.com, keescook@...omium.org, pavel@....cz, jinb.park7@...il.com, anisse@...ier.eu, rafael.j.wysocki@...el.com, zijun_hu@....com, mingo@...nel.org, mawilcox@...rosoft.com, thgarnie@...gle.com, joelaf@...gle.com, kirill.shutemov@...ux.intel.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, pankaj.m@...sung.com, ajeet.y@...sung.com, hakbong5.lee@...sung.com, a.sahrawat@...sung.com, lalit.mohan@...sung.com, cpgs@...sung.com, Vaneet Narang <v.narang@...sung.com> Subject: Re: [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
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