linux-kernel - Re: [PATCH] module: Refine kmemleak scanned areas

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Message-ID: <ZtxenHsGPyDoYnzY@arm.com>
Date: Sat, 7 Sep 2024 15:12:13 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Vincent Donnefort <vdonnefort@...gle.com>
Cc: mcgrof@...nel.org, linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-team@...roid.com,
	Song Liu <song@...nel.org>
Subject: Re: [PATCH] module: Refine kmemleak scanned areas

On Fri, Sep 06, 2024 at 04:38:56PM +0100, Vincent Donnefort wrote:
> commit ac3b43283923 ("module: replace module_layout with module_memory")
> introduced a set of memory regions for the module layout sharing the
> same attributes but didn't update the kmemleak scanned areas which
> intended to limit kmemleak scan to sections containing writable data.
> This means sections such as .text and .rodata are scanned by kmemleak.
> 
> Refine the scanned areas for modules by limiting it to MOD_TEXT and
> MOD_INIT_TEXT mod_mem regions.
> 
> CC: Song Liu <song@...nel.org>
> CC: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>
> 
> diff --git a/kernel/module/debug_kmemleak.c b/kernel/module/debug_kmemleak.c
> index 12a569d361e8..b4cc03842d70 100644
> --- a/kernel/module/debug_kmemleak.c
> +++ b/kernel/module/debug_kmemleak.c
> @@ -12,19 +12,9 @@
>  void kmemleak_load_module(const struct module *mod,
>  			  const struct load_info *info)
>  {
> -	unsigned int i;
> -
> -	/* only scan the sections containing data */
> -	kmemleak_scan_area(mod, sizeof(struct module), GFP_KERNEL);
> -
> -	for (i = 1; i < info->hdr->e_shnum; i++) {
> -		/* Scan all writable sections that's not executable */
> -		if (!(info->sechdrs[i].sh_flags & SHF_ALLOC) ||
> -		    !(info->sechdrs[i].sh_flags & SHF_WRITE) ||
> -		    (info->sechdrs[i].sh_flags & SHF_EXECINSTR))
> -			continue;
> -
> -		kmemleak_scan_area((void *)info->sechdrs[i].sh_addr,
> -				   info->sechdrs[i].sh_size, GFP_KERNEL);
> +	/* only scan writable, non-executable sections */
> +	for_each_mod_mem_type(type) {
> +		if (type != MOD_DATA && type != MOD_INIT_DATA)
> +			kmemleak_no_scan(mod->mem[type].base);
>  	}
>  }

I lost track of how module memory allocation works. Is struct module
still scanned after this change?

-- 
Catalin