Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1308719

Re: livepatch: reuse module loader code to write relocations

Show all headers | View raw

+++ Miroslav Benes [13/01/16 10:19 +0100]:
>On Fri, 8 Jan 2016, Jessica Yu wrote:
>
>>  static int klp_write_object_relocations(struct module *pmod,
>>  					struct klp_object *obj)
>>  {
>> -	int ret = 0;
>> -	unsigned long val;
>> -	struct klp_reloc *reloc;
>> +	int i, len, ret = 0;
>> +	char *secname;
>> +	const char *objname;
>>
>>  	if (WARN_ON(!klp_is_object_loaded(obj)))
>>  		return -EINVAL;
>>
>> -	if (WARN_ON(!obj->relocs))
>> -		return -EINVAL;
>> +	objname = klp_is_module(obj) ? obj->name : "vmlinux";
>>
>>  	module_disable_ro(pmod);
>> +	/* For each klp rela section for this object */
>> +	for (i = 1; i < pmod->info->hdr->e_shnum; i++) {
>> +		if (!(pmod->info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH))
>> +			continue;
>
>One more thing. If the module does not specify it is a live patch module
>in modinfo (with MODULE_INFO(livepatch, "Y")), but it is a perfect live
>patch module otherwise (it calls klp_register_patch in its init function),
>the kernel crashes here. pmod->info is not initialized at all. This should
>be fixed. Perhaps the easiest would be to call
>klp_write_object_relocations() in klp_init_object_loaded() only if
>is_livepatch_module() returns true. Similar to a check for obj->relocs
>before.

Hm yes, that's a problem. To remedy this, I think it makes sense to
require all livepatch modules to identify themselves with the modinfo
attribute, since it is a very simple requirement. If some module calls
klp_register_patch() and it does not have the livepatch attribute,
klp_register_patch() can just return an error. We can call
is_livepatch_module() at the beginning of klp_register_patch(), and
proceed only if the check succeeds, since we'll then know that the
required structures have been properly initialized in the module
loader. What do you think?

Jessica

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[RFC PATCH v3 0/6] (mostly) Arch-independent livepatch Jessica Yu <jeyu@redhat.com> - 2016-01-08 20:30 +0100
  [RFC PATCH v3 1/6] Elf: add livepatch-specific Elf constants Jessica Yu <jeyu@redhat.com> - 2016-01-08 20:30 +0100
  [RFC PATCH v3 3/6] module: s390: keep mod_arch_specific for livepatch modules Jessica Yu <jeyu@redhat.com> - 2016-01-08 20:30 +0100
  [RFC PATCH v3 5/6] samples: livepatch: mark as livepatch module Jessica Yu <jeyu@redhat.com> - 2016-01-08 20:30 +0100
  [RFC PATCH v3 4/6] livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2016-01-08 20:40 +0100
    Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write  relocations Petr Mladek <pmladek@suse.com> - 2016-01-11 18:00 +0100
      Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write  relocations Josh Poimboeuf <jpoimboe@redhat.com> - 2016-01-11 22:00 +0100
    Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write  relocations Josh Poimboeuf <jpoimboe@redhat.com> - 2016-01-11 22:40 +0100
      Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2016-01-11 23:40 +0100
        Re: livepatch: reuse module loader code to write relocations Josh Poimboeuf <jpoimboe@redhat.com> - 2016-01-12 04:10 +0100
          Re: livepatch: reuse module loader code to write relocations Petr Mladek <pmladek@suse.com> - 2016-01-12 10:20 +0100
          Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2016-01-14 06:10 +0100
    Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write  relocations Miroslav Benes <mbenes@suse.cz> - 2016-01-12 17:50 +0100
      Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2016-01-14 05:00 +0100
        Re: livepatch: reuse module loader code to write relocations Miroslav Benes <mbenes@suse.cz> - 2016-01-14 10:10 +0100
    Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write  relocations Miroslav Benes <mbenes@suse.cz> - 2016-01-13 10:20 +0100
      Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write  relocations Jiri Kosina <jikos@kernel.org> - 2016-01-13 10:40 +0100
      Re: livepatch: reuse module loader code to write relocations Jessica Yu <jeyu@redhat.com> - 2016-01-13 19:40 +0100
        Re: livepatch: reuse module loader code to write relocations Miroslav Benes <mbenes@suse.cz> - 2016-01-14 10:20 +0100

csiph-web