Re: [RFC v2 4/7] modsig: add integrity_module_check hook

[Kasatkin, Dmitry]

On Thu, Aug 16, 2012 at 12:13 AM, Kasatkin, Dmitry
<dmitry.kasatkin@xxxxxxxxx> wrote:
> On Wed, Aug 15, 2012 at 11:16 PM, Serge Hallyn
> <serge.hallyn@xxxxxxxxxxxxx> wrote:
>> Quoting Dmitry Kasatkin (dmitry.kasatkin@xxxxxxxxx):
>>> IMA measures/appraises modules when modprobe or insmod opens and read them.
>>> Unfortunately, there are no guarantees between what is read by userspace and
>>> what is passed to the kernel via load_module system call. This patch adds a
>>> hook called integrity_module_check() to verify the integrity of the module
>>> being loaded.
>>>
>>> Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
>>> ---
>>>  include/linux/integrity.h |   10 ++++++++++
>>>  kernel/module.c           |    9 +++++++++
>>>  2 files changed, 19 insertions(+)
>>>
>>> diff --git a/include/linux/integrity.h b/include/linux/integrity.h
>>> index 66c5fe9..a80ec06 100644
>>> --- a/include/linux/integrity.h
>>> +++ b/include/linux/integrity.h
>>> @@ -37,4 +37,14 @@ static inline void integrity_inode_free(struct inode *inode)
>>>       return;
>>>  }
>>>  #endif /* CONFIG_INTEGRITY_H */
>>> +
>>> +#ifdef CONFIG_INTEGRITY_MODULES
>>> +int integrity_module_check(const void *hdr, const unsigned long len);
>>
>> sadly not bisect-safe, since integrity_module_check() is defined in
>> the next patch.
>>
>
> Ok.. Hooks come after implementation...
> Will swap.
>

Hi Serge.

Actually Kconfig option is defined in following implementation patch,
so CONFIG_INTEGRITY_MODULES is not defined and it will compile inline
empty function.

Why is it not bisect-safe?

- Dmitry

> Thanks.
>
>>> +#else
>>> +static inline int integrity_module_check(const void *buf, unsigned long len)
>>> +{
>>> +     return 0;
>>> +}
>>> +#endif
>>> +
>>>  #endif /* _LINUX_INTEGRITY_H */
>>> diff --git a/kernel/module.c b/kernel/module.c
>>> index 4edbd9c..791da47 100644
>>> --- a/kernel/module.c
>>> +++ b/kernel/module.c
>>> @@ -58,6 +58,7 @@
>>>  #include <linux/jump_label.h>
>>>  #include <linux/pfn.h>
>>>  #include <linux/bsearch.h>
>>> +#include <linux/integrity.h>
>>>
>>>  #define CREATE_TRACE_POINTS
>>>  #include <trace/events/module.h>
>>> @@ -2437,6 +2438,14 @@ static int copy_and_check(struct load_info *info,
>>>
>>>       info->hdr = hdr;
>>>       info->len = len;
>>> +
>>> +     err = integrity_module_check(hdr, len);
>>> +     if (err < 0)
>>> +             goto free_hdr;
>>> +
>>> +     /* cut signature tail */
>>> +     info->len = err;
>>> +
>>>       return 0;
>>>
>>>  free_hdr:
>>> --
>>> 1.7.9.5
>>>
>>> --
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