[PATCH v1 4/8] kho: do not modify incoming serialized blocks

[Pasha Tatashin]

When restoring an incoming block set via kho_block_set_restore(), the
physical chain of blocks is already linked and bs->head_pa is already
set. However, kho_block_add() unconditionally rewrites last->ser->next
and bs->head_pa, and kho_block_set_shrink_one() clears
new_last->ser->next even when operating on an incoming block set.

In the upcoming KHO read-only mode, incoming serialized blocks are
mapped read-only and must not be modified. Guard the ser->next and
bs->head_pa updates in kho_block_add() and kho_block_set_shrink_one()
with !bs->incoming.

Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
---
 kernel/liveupdate/kho_block.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/liveupdate/kho_block.c b/kernel/liveupdate/kho_block.c
index 0d2a342ef422..a4e945f28fad 100644
--- a/kernel/liveupdate/kho_block.c
+++ b/kernel/liveupdate/kho_block.c
@@ -93,10 +93,12 @@ static int kho_block_add(struct kho_block_set *bs,
 	list_add_tail(&block->list, &bs->blocks);
 	bs->nblocks++;
 
-	if (last)
-		last->ser->next = virt_to_phys(ser);
-	else
-		bs->head_pa = virt_to_phys(ser);
+	if (!bs->incoming) {
+		if (last)
+			last->ser->next = virt_to_phys(ser);
+		else
+			bs->head_pa = virt_to_phys(ser);
+	}
 
 	return 0;
 }
@@ -133,10 +135,10 @@ static void kho_block_set_shrink_one(struct kho_block_set *bs)
 	kfree(last);
 
 	new_last = list_last_entry_or_null(&bs->blocks, struct kho_block, list);
-	if (new_last)
-		new_last->ser->next = 0;
-	else
+	if (!new_last)
 		bs->head_pa = 0;
+	else if (!bs->incoming)
+		new_last->ser->next = 0;
 }
 
 /**
-- 
2.56.0.176.g3575e65682-goog