[PATCH] mm/mseal: add comment explaining why we disallow gaps on mseal()

[Lorenzo Stoakes]

This explains the semantics clearly, the 'why' of the situation.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
 mm/mseal.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/mm/mseal.c b/mm/mseal.c
index 1059322add34..d140f569c4c3 100644
--- a/mm/mseal.c
+++ b/mm/mseal.c
@@ -37,6 +37,18 @@ static int mseal_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	return ret;
 }

+/*
+ * mseal() disallows an input range which contain unmapped ranges (VMA holes).
+ *
+ * It disallows unmapped regions from start to end whether they exist at the
+ * start, in the middle, or at the end of the range, or any combination thereof.
+ *
+ * This is because after sealng a range, there's nothing to stop memory mapping
+ * of ranges in the remaining gaps later, meaning that the user might then
+ * wrongly consider the entirety of the mseal()'d range to be sealed when it
+ * in fact isn't.
+ */
+
 /*
  * Does the [start, end) range contain any unmapped memory?
  *
--
2.50.1