Re: [PATCH 03/18] pstore: Avoid race in module unloading

[Kees Cook]

On Tue, Mar 7, 2017 at 8:16 AM, Namhyung Kim <namhyung@xxxxxxxxx> wrote:
> Hi Kees,
>
> On Tue, Mar 7, 2017 at 6:55 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> Technically, it might be possible for struct pstore_info to go out of
>> scope after the module_put(), so report the backend name first.
>
> But in that case, using pstore will crash the kernel anyway, right?
> If so, why pstore doesn't keep a reference until unregister?
> Do I miss something?

I could be wrong with this, since the backend can't call unregister
until register has finished... I'll drop this patch.

-Kees

>
> Thanks,
> Namhyung
>
>
>>
>> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
>> ---
>>  fs/pstore/platform.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
>> index 074fe85a2078..d69ef8a840b9 100644
>> --- a/fs/pstore/platform.c
>> +++ b/fs/pstore/platform.c
>> @@ -722,10 +722,10 @@ int pstore_register(struct pstore_info *psi)
>>          */
>>         backend = psi->name;
>>
>> -       module_put(owner);
>> -
>>         pr_info("Registered %s as persistent store backend\n", psi->name);
>>
>> +       module_put(owner);
>> +
>>         return 0;
>>  }
>>  EXPORT_SYMBOL_GPL(pstore_register);
>> --
>> 2.7.4
>>



-- 
Kees Cook
Pixel Security