diff --git a/mm/mmap.c b/mm/mmap.c
index c30ebe82ebdb..9f76625a1743 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1726,7 +1726,7 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
 	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
 }
 
-unsigned long mmap_region(struct file *file, unsigned long addr,
+static unsigned long __mmap_region(struct file *file, unsigned long addr,
 		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
 		struct list_head *uf)
 {
@@ -1795,11 +1795,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 			if (error)
 				goto free_vma;
 		}
-		if (vm_flags & VM_SHARED) {
-			error = mapping_map_writable(file->f_mapping);
-			if (error)
-				goto allow_write_and_free_vma;
-		}
 
 		/* ->mmap() can change vma->vm_file, but must guarantee that
 		 * vma_link() below can deny write-access if VM_DENYWRITE is set
@@ -1809,7 +1804,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		vma->vm_file = get_file(file);
 		error = mmap_file(file, vma);
 		if (error)
-			goto unmap_and_free_vma;
+			goto unmap_and_free_file_vma;
 
 		/* Can addr have changed??
 		 *
@@ -1820,6 +1815,14 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		 */
 		WARN_ON_ONCE(addr != vma->vm_start);
 
+		/*
+		 * Drivers should not permit writability when previously it was
+		 * disallowed.
+		 */
+		VM_WARN_ON_ONCE(vm_flags != vma->vm_flags &&
+				!(vm_flags & VM_MAYWRITE) &&
+				(vma->vm_flags & VM_MAYWRITE));
+
 		addr = vma->vm_start;
 
 		/* If vm_flags changed after mmap_file(), we should try merge vma again
@@ -1851,21 +1854,14 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		vma_set_anonymous(vma);
 	}
 
-	/* Allow architectures to sanity-check the vm_flags */
-	if (!arch_validate_flags(vma->vm_flags)) {
-		error = -EINVAL;
-		if (file)
-			goto close_and_free_vma;
-		else
-			goto free_vma;
-	}
+#ifdef CONFIG_SPARC64
+	/* TODO: Fix SPARC ADI! */
+	WARN_ON_ONCE(!arch_validate_flags(vm_flags));
+#endif
 
 	vma_link(mm, vma, prev, rb_link, rb_parent);
-	/* Once vma denies write, undo our temporary denial count */
 	if (file) {
 unmap_writable:
-		if (vm_flags & VM_SHARED)
-			mapping_unmap_writable(file->f_mapping);
 		if (vm_flags & VM_DENYWRITE)
 			allow_write_access(file);
 	}
@@ -1899,17 +1895,12 @@ out:
 
 	return addr;
 
-close_and_free_vma:
-	vma_close(vma);
-unmap_and_free_vma:
+unmap_and_free_file_vma:
 	vma->vm_file = NULL;
 	fput(file);
 
 	/* Undo any partial mapping done by a device driver. */
 	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
-	if (vm_flags & VM_SHARED)
-		mapping_unmap_writable(file->f_mapping);
-allow_write_and_free_vma:
 	if (vm_flags & VM_DENYWRITE)
 		allow_write_access(file);
 free_vma:
@@ -2931,6 +2922,36 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	return __do_munmap(mm, start, len, uf, false);
 }
 
+unsigned long mmap_region(struct file *file, unsigned long addr,
+			  unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
+			  struct list_head *uf)
+{
+	unsigned long ret;
+	bool writable_file_mapping = false;
+
+	/* Allow architectures to sanity-check the vm_flags. */
+	if (!arch_validate_flags(vm_flags))
+		return -EINVAL;
+
+	/* Map writable and ensure this isn't a sealed memfd. */
+	if (file && (vm_flags & VM_SHARED)) {
+		int error = mapping_map_writable(file->f_mapping);
+
+		if (error)
+			return error;
+		writable_file_mapping = true;
+	}
+
+	ret = __mmap_region(file, addr, len, vm_flags, pgoff, uf);
+
+	/* Clear our write mapping regardless of error. */
+	if (writable_file_mapping)
+		mapping_unmap_writable(file->f_mapping);
+
+	validate_mm(current->mm);
+	return ret;
+}
+
 static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
 {
 	int ret;