[RFC PATCH 3/7] module: prepare to handle ROX allocations for text

[Nadav Amit]

> On 11 Apr 2024, at 19:05, Mike Rapoport <rppt at kernel.org> wrote:
> 
> @@ -2440,7 +2479,24 @@ static int post_relocation(struct module *mod, const struct load_info *info)
> 	add_kallsyms(mod, info);
> 
> 	/* Arch-specific module finalizing. */
> -	return module_finalize(info->hdr, info->sechdrs, mod);
> +	ret = module_finalize(info->hdr, info->sechdrs, mod);
> +	if (ret)
> +		return ret;
> +
> +	for_each_mod_mem_type(type) {
> +		struct module_memory *mem = &mod->mem[type];
> +
> +		if (mem->is_rox) {
> +			if (!execmem_update_copy(mem->base, mem->rw_copy,
> +						 mem->size))
> +				return -ENOMEM;
> +
> +			vfree(mem->rw_copy);
> +			mem->rw_copy = NULL;
> +		}
> +	}
> +
> +	return 0;
> }

I might be missing something, but it seems a bit racy.

IIUC, module_finalize() calls alternatives_smp_module_add(). At this
point, since you don’t hold the text_mutex, some might do text_poke(),
e.g., by enabling/disabling static-key, and the update would be
overwritten. No?