Re: [PATCH bpf] bpf, lsm: Fix the file_mprotect LSM test.

[Alexei Starovoitov]

On Thu, Apr 2, 2020 at 1:07 PM KP Singh <kpsingh@xxxxxxxxxxxx> wrote:
>
> From: KP Singh <kpsingh@xxxxxxxxxx>
>
> The test was previously using an mprotect on the heap memory allocated
> using malloc and was expecting the allocation to be always using
> sbrk(2). This is, however, not always true and in certain conditions
> malloc may end up using anonymous mmaps for heap alloctions. This means
> that the following condition that is used in the "lsm/file_mprotect"
> program is not sufficent to detect all mprotect calls done on heap
> memory:
>
>         is_heap = (vma->vm_start >= vma->vm_mm->start_brk &&
>                    vma->vm_end <= vma->vm_mm->brk);
>
> The test is updated to use an mprotect on memory allocated on the stack.
> While this would result in the splitting of the vma, this happens only
> after the security_file_mprotect hook. So, the condition used in the BPF
> program holds true.
>
> Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
> Reported-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> Fixes: 03e54f100d57 ("bpf: lsm: Add selftests for BPF_PROG_TYPE_LSM")

Applied. Thanks