Re: [RFC 08/12] mm: Track VMA's in use for each memory encryption keyid

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Fri, 2018-09-07 at 15:37 -0700, Alison Schofield wrote:
> Keep track of the VMA's oustanding for each memory encryption keyid.
> The count is used by the MKTME (Multi-Key Total Memory Encryption)
> Key Service to determine when it is safe to reprogram a hardware
> encryption key.

Maybe a stupid question but why they are tracked and what do you 
mean by tracking?

/Jarkko

> Approach here is to do gets and puts on the encryption reference
> wherever kmem_cache_alloc/free's of vma_area_cachep's are executed.
> A couple of these locations will not be hit until cgroup support is
> added. One of these locations should never hit, so use a VM_WARN_ON.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> ---
>  arch/x86/mm/mktme.c |  2 ++
>  kernel/fork.c       |  2 ++
>  mm/mmap.c           | 12 ++++++++++++
>  mm/nommu.c          |  4 ++++
>  4 files changed, 20 insertions(+)
> 
> diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
> index 5690ef51a79a..8a7c326d4546 100644
> --- a/arch/x86/mm/mktme.c
> +++ b/arch/x86/mm/mktme.c
> @@ -72,10 +72,12 @@ void mprotect_set_encrypt(struct vm_area_struct *vma, int
> newkeyid)
>  	if (newkeyid == oldkeyid)
>  		return;
>  
> +	vma_put_encrypt_ref(vma);
>  	newprot = pgprot_val(vma->vm_page_prot);
>  	newprot &= ~mktme_keyid_mask;
>  	newprot |= (unsigned long)newkeyid << mktme_keyid_shift;
>  	vma->vm_page_prot = __pgprot(newprot);
> +	vma_get_encrypt_ref(vma);
>  }
>  
>  /*
> diff --git a/kernel/fork.c b/kernel/fork.c
> index e5e7a220a124..2d0e507bde7c 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -459,6 +459,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
>  		if (!tmp)
>  			goto fail_nomem;
>  		*tmp = *mpnt;
> +		vma_get_encrypt_ref(tmp);	/* Track encrypted vma's */
>  		INIT_LIST_HEAD(&tmp->anon_vma_chain);
>  		retval = vma_dup_policy(mpnt, tmp);
>  		if (retval)
> @@ -539,6 +540,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
>  fail_nomem_anon_vma_fork:
>  	mpol_put(vma_policy(tmp));
>  fail_nomem_policy:
> +	vma_put_encrypt_ref(tmp);		/* Track encrypted vma's */
>  	kmem_cache_free(vm_area_cachep, tmp);
>  fail_nomem:
>  	retval = -ENOMEM;
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 4c604eb644b4..7390b8b69fd6 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -182,6 +182,7 @@ static struct vm_area_struct *remove_vma(struct
> vm_area_struct *vma)
>  	if (vma->vm_file)
>  		fput(vma->vm_file);
>  	mpol_put(vma_policy(vma));
> +	vma_put_encrypt_ref(vma);
>  	kmem_cache_free(vm_area_cachep, vma);
>  	return next;
>  }
> @@ -913,6 +914,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long
> start,
>  			anon_vma_merge(vma, next);
>  		mm->map_count--;
>  		mpol_put(vma_policy(next));
> +		vma_put_encrypt_ref(next);
>  		kmem_cache_free(vm_area_cachep, next);
>  		/*
>  		 * In mprotect's case 6 (see comments on vma_merge),
> @@ -1744,6 +1746,7 @@ unsigned long mmap_region(struct file *file, unsigned
> long addr,
>  		goto unacct_error;
>  	}
>  
> +	vma_get_encrypt_ref(vma);
>  	vma->vm_mm = mm;
>  	vma->vm_start = addr;
>  	vma->vm_end = addr + len;
> @@ -1839,6 +1842,7 @@ unsigned long mmap_region(struct file *file, unsigned
> long addr,
>  unmap_and_free_vma:
>  	vma->vm_file = NULL;
>  	fput(file);
> +	vma_put_encrypt_ref(vma);
>  
>  	/* Undo any partial mapping done by a device driver. */
>  	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
> @@ -2653,6 +2657,7 @@ int __split_vma(struct mm_struct *mm, struct
> vm_area_struct *vma,
>  		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
>  	}
>  
> +	vma_get_encrypt_ref(new);
>  	err = vma_dup_policy(vma, new);
>  	if (err)
>  		goto out_free_vma;
> @@ -2686,6 +2691,7 @@ int __split_vma(struct mm_struct *mm, struct
> vm_area_struct *vma,
>   out_free_mpol:
>  	mpol_put(vma_policy(new));
>   out_free_vma:
> +	vma_put_encrypt_ref(new);
>  	kmem_cache_free(vm_area_cachep, new);
>  	return err;
>  }
> @@ -3007,6 +3013,7 @@ static int do_brk_flags(unsigned long addr, unsigned
> long len, unsigned long fla
>  		return -ENOMEM;
>  	}
>  
> +	vma_get_encrypt_ref(vma);
>  	INIT_LIST_HEAD(&vma->anon_vma_chain);
>  	vma->vm_mm = mm;
>  	vma->vm_ops = &anon_vm_ops;
> @@ -3229,6 +3236,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct
> **vmap,
>  		new_vma->vm_pgoff = pgoff;
>  		if (vma_dup_policy(vma, new_vma))
>  			goto out_free_vma;
> +		vma_get_encrypt_ref(new_vma);
>  		INIT_LIST_HEAD(&new_vma->anon_vma_chain);
>  		if (anon_vma_clone(new_vma, vma))
>  			goto out_free_mempol;
> @@ -3243,6 +3251,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct
> **vmap,
>  
>  out_free_mempol:
>  	mpol_put(vma_policy(new_vma));
> +	vma_put_encrypt_ref(new_vma);
>  out_free_vma:
>  	kmem_cache_free(vm_area_cachep, new_vma);
>  out:
> @@ -3372,6 +3381,9 @@ static struct vm_area_struct *__install_special_mapping(
>  	if (unlikely(vma == NULL))
>  		return ERR_PTR(-ENOMEM);
>  
> +	/* Do not expect a memory encrypted vma here */
> +	VM_WARN_ON(vma_keyid(vma));
> +
>  	INIT_LIST_HEAD(&vma->anon_vma_chain);
>  	vma->vm_mm = mm;
>  	vma->vm_start = addr;
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 73f66e81cfb0..85f04c174638 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -769,6 +769,7 @@ static void delete_vma(struct mm_struct *mm, struct
> vm_area_struct *vma)
>  	if (vma->vm_file)
>  		fput(vma->vm_file);
>  	put_nommu_region(vma->vm_region);
> +	vma_put_encrypt_ref(vma);
>  	kmem_cache_free(vm_area_cachep, vma);
>  }
>  
> @@ -1215,6 +1216,7 @@ unsigned long do_mmap(struct file *file,
>  	if (!vma)
>  		goto error_getting_vma;
>  
> +	vma_get_encrypt_ref(vma);
>  	region->vm_usage = 1;
>  	region->vm_flags = vm_flags;
>  	region->vm_pgoff = pgoff;
> @@ -1375,6 +1377,7 @@ unsigned long do_mmap(struct file *file,
>  	kmem_cache_free(vm_region_jar, region);
>  	if (vma->vm_file)
>  		fput(vma->vm_file);
> +	vma_put_encrypt_ref(vma);
>  	kmem_cache_free(vm_area_cachep, vma);
>  	return ret;
>  
> @@ -1486,6 +1489,7 @@ int split_vma(struct mm_struct *mm, struct
> vm_area_struct *vma,
>  	*new = *vma;
>  	*region = *vma->vm_region;
>  	new->vm_region = region;
> +	vma_get_encrypt_ref(new);
>  
>  	npages = (addr - vma->vm_start) >> PAGE_SHIFT;
>