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

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Date:   Tue, 4 Apr 2023 23:52:22 -0700
From:   Song Liu <song@...nel.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
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, 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, catalin.marinas@....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 4, 2023 at 7:27 PM Luis Chamberlain <mcgrof@...nel.org> wrote:
>
> Commit ac3b43283923 ("module: replace module_layout with module_memory")
> reworked the way to handle memory allocations to make it clearer. But it
> lost in translation how we handled kmemleak_ignore() or kmemleak_not_leak()
> for different ELF sections.
>
> Fix this and clarify the comments a bit more.
>
> Fixes: ac3b43283923 ("module: replace module_layout with module_memory")
> Reported-by: Jim Cromie <jim.cromie@...il.com>
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>

Acked-by: Song Liu <song@...nel.org>

Thanks for the fix!

> ---
>  kernel/module/main.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
>
> 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);
> +               }
>                 if (!ptr) {
>                         t = type;
>                         goto out_enomem;
> --
> 2.39.2
>