On Tue, Apr 16, 2024 at 12:36:08PM +0300, Nadav Amit wrote:
>
>
> > On 11 Apr 2024, at 19:05, Mike Rapoport <rppt@xxxxxxxxxx> 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?
Right :(
Even worse, for UP case alternatives_smp_unlock() will "patch" still empty
area.
So I'm thinking about calling alternatives_smp_module_add() from an
additional callback after the execmem_update_copy().
Does it make sense to you?
--
Sincerely yours,
Mike.
