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    Subject[PATCH v36 10/24] mm: Add vm_ops->mprotect()
    Date
    From: Sean Christopherson <sean.j.christopherson@intel.com>

    Add vm_ops()->mprotect() for additional constraints for a VMA.

    Intel Software Guard eXtensions (SGX) will use this callback to add two
    constraints:

    1. Verify that the address range does not have holes: each page address
    must be filled with an enclave page.
    2. Verify that VMA permissions won't surpass the permissions of any enclave
    page within the address range. Enclave cryptographically sealed
    permissions for each page address that set the upper limit for possible
    VMA permissions. Not respecting this can cause #GP's to be emitted.

    Cc: linux-mm@kvack.org
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Matthew Wilcox <willy@infradead.org>
    Acked-by: Jethro Beekman <jethro@fortanix.com>
    Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    ---
    include/linux/mm.h | 3 +++
    mm/mprotect.c | 5 ++++-
    2 files changed, 7 insertions(+), 1 deletion(-)

    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index dc7b87310c10..458e8cb99aaf 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -542,6 +542,9 @@ 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 (*mprotect)(struct vm_area_struct *vma,
    + struct vm_area_struct **pprev, unsigned long start,
    + unsigned long end, unsigned long newflags);
    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..f170f3da8a4f 100644
    --- a/mm/mprotect.c
    +++ b/mm/mprotect.c
    @@ -610,7 +610,10 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
    tmp = vma->vm_end;
    if (tmp > end)
    tmp = end;
    - error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
    + if (vma->vm_ops && vma->vm_ops->mprotect)
    + error = vma->vm_ops->mprotect(vma, &prev, nstart, tmp, newflags);
    + else
    + error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
    if (error)
    goto out;
    nstart = tmp;
    --
    2.25.1
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