[RFC PATCH v1] ima: verify mprotect change is consistent with mmap policy

[Lakshmi Ramasubramanian]

On 5/5/20 10:30 AM, Mimi Zohar wrote:

> Files can be mmap'ed read/write and later changed to execute to circumvent
> IMA's mmap appraise policy rules.  Due to locking issues (mmap semaphore
> would be taken prior to i_mutex), files can not be measured or appraised at
> this point.  Eliminate this integrity gap, by denying the mprotect
> PROT_EXECUTE change, if an mmap appraise policy rule exists.
> 
> On mprotect change success, return 0.  On failure, return -EACESS.
> 
> Signed-off-by: Mimi Zohar <zohar at linux.ibm.com>
> ---
> Changelog v1:
> - Reverse tests to remove code indentation. (Lakshmi Ramasubramanian)
> - General code cleanup, including adding comments.
> 
>   include/linux/ima.h               |  7 ++++++
>   security/integrity/ima/ima_main.c | 51 +++++++++++++++++++++++++++++++++++++++
>   security/security.c               |  7 +++++-
>   3 files changed, 64 insertions(+), 1 deletion(-)

Reviewed-by: Lakshmi Ramasubramanian <nramas at linux.microsoft.com>