linux-kernel - Re: [PATCH v2 1/6] module: fix kmemleak annotations for non init ELF sections

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Date:   Tue, 11 Apr 2023 10:06:24 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     david@...hat.com, patches@...ts.linux.dev,
        linux-modules@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, pmladek@...e.com,
        petr.pavlu@...e.com, prarit@...hat.com,
        torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
        rafael@...nel.org, christophe.leroy@...roup.eu, tglx@...utronix.de,
        peterz@...radead.org, song@...nel.org, rppt@...nel.org,
        dave@...olabs.net, willy@...radead.org, vbabka@...e.cz,
        mhocko@...e.com, dave.hansen@...ux.intel.com,
        colin.i.king@...il.com, jim.cromie@...il.com, jbaron@...mai.com,
        rick.p.edgecombe@...el.com
Subject: Re: [PATCH v2 1/6] module: fix kmemleak annotations for non init ELF
 sections

On Tue, Apr 11, 2023 at 04:17:35PM +0100, Catalin Marinas wrote:
> On Tue, Apr 04, 2023 at 07:26:57PM -0700, Luis Chamberlain wrote:
> > diff --git a/kernel/module/main.c b/kernel/module/main.c
> > index 5cc21083af04..d8bb23fa6989 100644
> > --- a/kernel/module/main.c
> > +++ b/kernel/module/main.c
> > @@ -2233,11 +2233,23 @@ static int move_module(struct module *mod, struct load_info *info)
> >  		ptr = module_memory_alloc(mod->mem[type].size, type);
> >  
> >  		/*
> > -		 * The pointer to this block is stored in the module structure
> > -		 * which is inside the block. Just mark it as not being a
> > -		 * leak.
> > +		 * The pointer to these blocks of memory are stored on the module
> > +		 * structure and we keep that around so long as the module is
> > +		 * around. We only free that memory when we unload the module.
> > +		 * Just mark them as not being a leak then. The .init* ELF
> > +		 * sections *do* get freed after boot so we treat them slightly
> > +		 * differently and only grey them out -- they work as typical
> > +		 * memory allocations which *do* eventually get freed.
> >  		 */
> > -		kmemleak_ignore(ptr);
> > +		switch (type) {
> > +		case MOD_INIT_TEXT: /* fallthrough */
> > +		case MOD_INIT_DATA: /* fallthrough */
> > +		case MOD_INIT_RODATA: /* fallthrough */
> > +			kmemleak_ignore(ptr);
> > +			break;
> > +		default:
> > +			kmemleak_not_leak(ptr);
> > +		}
> 
> This works as well but if you want to keep it simple, just call
> kmemleak_not_leak() in all cases. When freeing the init sections, they
> would be removed from the kmemleak tracing anyway.

It is up to you as you were the one who originally used different calls
here, so I didn't want to change the old mechanism. Changing it to use
kmemleak_not_leak() would be a functional change, do we loose anything
for using kmemleak_not_leak() for all? Ie, why had you used a different
set of calls when you first added this depending on the if its init or
not? Is the value no longer there?

  Luis