[PATCH v2 02/17] mm: Exempt special mappings from mlock(), mprotect() and madvise()

[Peter Zijlstra <peterz@infradead.org>]

[-- Attachment #1: peterz-vm-no-special-mapping.patch --]
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It makes no sense to ever prod at special mappings with any of these
syscalls.

XXX should we include munmap() ?

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 mm/madvise.c  |    3 +++
 mm/mlock.c    |    3 ++-
 mm/mprotect.c |    3 +++
 3 files changed, 8 insertions(+), 1 deletion(-)

--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -678,6 +678,9 @@ static long
 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 		unsigned long start, unsigned long end, int behavior)
 {
+	if (vma_is_special_mapping(vma))
+		return -EINVAL;
+
 	switch (behavior) {
 	case MADV_REMOVE:
 		return madvise_remove(vma, prev, start, end);
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -521,7 +521,8 @@ static int mlock_fixup(struct vm_area_st
 	vm_flags_t old_flags = vma->vm_flags;
 
 	if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
-	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
+	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
+	    vma_is_special_mapping(vma))
 		/* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
 		goto out;
 
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -307,6 +307,9 @@ mprotect_fixup(struct vm_area_struct *vm
 		return 0;
 	}
 
+	if (vma_is_special_mapping(vma))
+		return -ENOMEM;
+
 	/*
 	 * If we make a private mapping writable we increase our commit;
 	 * but (without finer accounting) cannot reduce our commit if we


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