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SubjectRe: [PATCH, RFC 45/62] mm: Add the encrypt_mprotect() system call for MKTME
On Wed, May 08, 2019 at 05:44:05PM +0300, Kirill A. Shutemov wrote:

> @@ -347,7 +348,8 @@ static int prot_none_walk(struct vm_area_struct *vma, unsigned long start,
>
> int
> mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
> - unsigned long start, unsigned long end, unsigned long newflags)
> + unsigned long start, unsigned long end, unsigned long newflags,
> + int newkeyid)
> {
> struct mm_struct *mm = vma->vm_mm;
> unsigned long oldflags = vma->vm_flags;
> @@ -357,7 +359,14 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
> int error;
> int dirty_accountable = 0;
>
> - if (newflags == oldflags) {
> + /*
> + * Flags match and Keyids match or we have NO_KEY.
> + * This _fixup is usually called from do_mprotect_ext() except
> + * for one special case: caller fs/exec.c/setup_arg_pages()
> + * In that case, newkeyid is passed as -1 (NO_KEY).
> + */
> + if (newflags == oldflags &&
> + (newkeyid == vma_keyid(vma) || newkeyid == NO_KEY)) {
> *pprev = vma;
> return 0;
> }
> @@ -423,6 +432,8 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
> }
>
> success:
> + if (newkeyid != NO_KEY)
> + mprotect_set_encrypt(vma, newkeyid, start, end);
> /*
> * vm_flags and vm_page_prot are protected by the mmap_sem
> * held in write mode.
> @@ -454,10 +465,15 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
> }
>
> /*
> - * When pkey==NO_KEY we get legacy mprotect behavior here.
> + * do_mprotect_ext() supports the legacy mprotect behavior plus extensions
> + * for Protection Keys and Memory Encryption Keys. These extensions are
> + * mutually exclusive and the behavior is:
> + * (pkey==NO_KEY && keyid==NO_KEY) ==> legacy mprotect
> + * (pkey is valid) ==> legacy mprotect plus Protection Key extensions
> + * (keyid is valid) ==> legacy mprotect plus Encryption Key extensions
> */
> static int do_mprotect_ext(unsigned long start, size_t len,
> - unsigned long prot, int pkey)
> + unsigned long prot, int pkey, int keyid)
> {
> unsigned long nstart, end, tmp, reqprot;
> struct vm_area_struct *vma, *prev;
> @@ -555,7 +571,8 @@ static int do_mprotect_ext(unsigned long start, size_t len,
> tmp = vma->vm_end;
> if (tmp > end)
> tmp = end;
> - error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
> + error = mprotect_fixup(vma, &prev, nstart, tmp, newflags,
> + keyid);
> if (error)
> goto out;
> nstart = tmp;

I've missed the part where pkey && keyid results in a WARN or error or
whatever.

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