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Subject: Re: [RFC PATCH 3/7] module: prepare to handle ROX allocations for
 text
From: Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20240411160526.2093408-4-rppt@kernel.org>
Date: Tue, 16 Apr 2024 12:36:08 +0300
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To: Mike Rapoport <rppt@kernel.org>


> On 11 Apr 2024, at 19:05, Mike Rapoport <rppt@kernel.org> wrote:
>=20
> @@ -2440,7 +2479,24 @@ static int post_relocation(struct module *mod, =
const struct load_info *info)
> 	add_kallsyms(mod, info);
>=20
> 	/* Arch-specific module finalizing. */
> -	return module_finalize(info->hdr, info->sechdrs, mod);
> +	ret =3D module_finalize(info->hdr, info->sechdrs, mod);
> +	if (ret)
> +		return ret;
> +
> +	for_each_mod_mem_type(type) {
> +		struct module_memory *mem =3D &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 =3D 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=E2=80=99t hold the text_mutex, some might do =
text_poke(),
e.g., by enabling/disabling static-key, and the update would be
overwritten. No?=