mm: change mprotect_fixup to vma iterator

Use the vma iterator so that the iterator can be invalidated or updated to
avoid each caller doing so.

Link: https://lkml.kernel.org/r/20230120162650.984577-18-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/exec.c

@@ -758,6 +758,7 @@ int setup_arg_pages(struct linux_binprm *bprm,
 	unsigned long stack_expand;
 	unsigned long rlim_stack;
 	struct mmu_gather tlb;
+	struct vma_iterator vmi;
 
 #ifdef CONFIG_STACK_GROWSUP
 	/* Limit stack size */
@@ -812,8 +813,10 @@ int setup_arg_pages(struct linux_binprm *bprm,
 	vm_flags |= mm->def_flags;
 	vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 
+	vma_iter_init(&vmi, mm, vma->vm_start);
+
 	tlb_gather_mmu(&tlb, mm);
-	ret = mprotect_fixup(&tlb, vma, &prev, vma->vm_start, vma->vm_end,
+	ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
 			vm_flags);
 	tlb_finish_mmu(&tlb);
 

include/linux/mm.h

@@ -2197,9 +2197,9 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
 extern long change_protection(struct mmu_gather *tlb,
 			      struct vm_area_struct *vma, unsigned long start,
 			      unsigned long end, unsigned long cp_flags);
-extern int mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
+extern int mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
-			  struct vm_area_struct **pprev, unsigned long start,
+	  struct vm_area_struct *vma, struct vm_area_struct **pprev,
-			  unsigned long end, unsigned long newflags);
+	  unsigned long start, unsigned long end, unsigned long newflags);
 
 /*
  * doesn't attempt to fault and will return short.

mm/mprotect.c

@@ -585,9 +585,9 @@ static const struct mm_walk_ops prot_none_walk_ops = {
 };
 
 int
-mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
+mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
-	       struct vm_area_struct **pprev, unsigned long start,
+	       struct vm_area_struct *vma, struct vm_area_struct **pprev,
-	       unsigned long end, unsigned long newflags)
+	       unsigned long start, unsigned long end, unsigned long newflags)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long oldflags = vma->vm_flags;
@@ -642,7 +642,7 @@ mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	 * First try to merge with previous and/or next vma.
 	 */
 	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
-	*pprev = vma_merge(mm, *pprev, start, end, newflags,
+	*pprev = vmi_vma_merge(vmi, mm, *pprev, start, end, newflags,
 			   vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
 			   vma->vm_userfaultfd_ctx, anon_vma_name(vma));
 	if (*pprev) {
@@ -654,13 +654,13 @@ mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	*pprev = vma;
 
 	if (start != vma->vm_start) {
-		error = split_vma(mm, vma, start, 1);
+		error = vmi_split_vma(vmi, mm, vma, start, 1);
 		if (error)
 			goto fail;
 	}
 
 	if (end != vma->vm_end) {
-		error = split_vma(mm, vma, end, 0);
+		error = vmi_split_vma(vmi, mm, vma, end, 0);
 		if (error)
 			goto fail;
 	}
@@ -709,7 +709,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 	const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 				(prot & PROT_READ);
 	struct mmu_gather tlb;
-	MA_STATE(mas, &current->mm->mm_mt, 0, 0);
+	struct vma_iterator vmi;
 
 	start = untagged_addr(start);
 
@@ -741,8 +741,8 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 	if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 		goto out;
 
-	mas_set(&mas, start);
+	vma_iter_init(&vmi, current->mm, start);
-	vma = mas_find(&mas, ULONG_MAX);
+	vma = vma_find(&vmi, end);
 	error = -ENOMEM;
 	if (!vma)
 		goto out;
@@ -765,18 +765,22 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		}
 	}
 
+	prev = vma_prev(&vmi);
 	if (start > vma->vm_start)
 		prev = vma;
-	else
-		prev = mas_prev(&mas, 0);
 
 	tlb_gather_mmu(&tlb, current->mm);
-	for (nstart = start ; ; ) {
+	nstart = start;
+	tmp = vma->vm_start;
+	for_each_vma_range(vmi, vma, end) {
 		unsigned long mask_off_old_flags;
 		unsigned long newflags;
 		int new_vma_pkey;
 
-		/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
+		if (vma->vm_start != tmp) {
+			error = -ENOMEM;
+			break;
+		}
 
 		/* Does the application expect PROT_READ to imply PROT_EXEC */
 		if (rier && (vma->vm_flags & VM_MAYEXEC))
@@ -824,25 +828,18 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 				break;
 		}
 
-		error = mprotect_fixup(&tlb, vma, &prev, nstart, tmp, newflags);
+		error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags);
 		if (error)
 			break;
 
 		nstart = tmp;
-
-		if (nstart < prev->vm_end)
-			nstart = prev->vm_end;
-		if (nstart >= end)
-			break;
-
-		vma = find_vma(current->mm, prev->vm_end);
-		if (!vma || vma->vm_start != nstart) {
-			error = -ENOMEM;
-			break;
-		}
 		prot = reqprot;
 	}
 	tlb_finish_mmu(&tlb);
+
+	if (vma_iter_end(&vmi) < end)
+		error = -ENOMEM;
+
 out:
 	mmap_write_unlock(current->mm);
 	return error;