Re: [PATCH v33 10/21] mm: Introduce vm_ops->may_mprotect()

Borislav Petkov
2020-06-25T17:14:21Z

On Thu, Jun 18, 2020 at 01:08:32AM +0300, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Add vm_ops()->may_mprotect() to check additional constraints.
>
> SGX uses this callback to add two constraints:
>
> 1. Verify that the address range does not have holes: for each page
> address, there is an actual enclave page created.
> 2. Mapped permissions do not surpass the lowest enclave page permissions
> in the address range.
>
> linux-mm@kvack.org
> Andrew Morton <akpm@linux-foundation.org>

Something ate the Cc:s. Lemme add the mm list, akpm is already on Cc.

Leaving in the rest for mm folks.

> Acked-by: Jethro Beekman <jethro@fortanix.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
> include/linux/mm.h | 2 ++
> mm/mprotect.c | 14 +++++++++++---
> 2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index dc7b87310c10..be40b9c29327 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -542,6 +542,8 @@ struct vm_operations_struct {
> void (*close)(struct vm_area_struct * area);
> int (*split)(struct vm_area_struct * area, unsigned long addr);
> int (*mremap)(struct vm_area_struct * area);
> + int (*may_mprotect)(struct vm_area_struct *vma, unsigned long start,
> + unsigned long end, unsigned long prot);
> vm_fault_t (*fault)(struct vm_fault *vmf);
> vm_fault_t (*huge_fault)(struct vm_fault *vmf,
> enum page_entry_size pe_size);
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index ce8b8a5eacbb..f7731dc13ff0 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -603,13 +603,21 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
> goto out;
> }
>
> + tmp = vma->vm_end;
> + if (tmp > end)
> + tmp = end;
> +
> + if (vma->vm_ops && vma->vm_ops->may_mprotect) {
> + error = vma->vm_ops->may_mprotect(vma, nstart, tmp,
> + prot);
> + if (error)
> + goto out;
> + }
> +
> error = security_file_mprotect(vma, reqprot, prot);
> if (error)
> goto out;
>
> - tmp = vma->vm_end;
> - if (tmp > end)
> - tmp = end;
> error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
> if (error)
> goto out;
> --
> 2.25.1
>

--
Regards/Gruss,
Boris.