Re: [PATCH] module: Refine kmemleak scanned areas

[Vincent Donnefort <vdonnefort@google.com>]

On Sat, Sep 07, 2024 at 03:12:13PM +0100, Catalin Marinas wrote:
> 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@kernel.org>
> > CC: Catalin Marinas <catalin.marinas@arm.com>
> > Signed-off-by: Vincent Donnefort <vdonnefort@google.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?

That section being RW, it will be part of the MOD_DATA vmalloc and scanned.

-- 
Vincent

> 
> -- 
> Catalin