[Qemu-block] [PATCH v6 08/17] qcow2/overlaps: Protect active L2 tables

[Max Reitz]

Keep track of the active L2 tables in the metadata list to protect them
against accidental modifications.

Signed-off-by: Max Reitz <address@hidden>
---
 block/qcow2-cluster.c  |  2 ++
 block/qcow2-refcount.c |  6 ++++++
 block/qcow2-snapshot.c | 21 +++++++++++++++++++++
 block/qcow2.c          |  8 +++++++-
 4 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index b95f6fe..ec42602 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -285,6 +285,8 @@ static int l2_allocate(BlockDriverState *bs, int l1_index, 
uint64_t **table)
         goto fail;
     }
 
+    qcow2_metadata_list_enter(bs, l2_offset, 1, QCOW2_OL_ACTIVE_L2);
+
     *table = l2_table;
     trace_qcow2_l2_allocate_done(bs, l1_index, 0);
     return 0;
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 13799c8..76dd2bc 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1209,6 +1209,12 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
                 if (ret < 0) {
                     goto fail;
                 }
+                if (addend < 0) {
+                    if (!l1_allocated) {
+                        qcow2_metadata_list_remove(bs, l2_offset, 1,
+                                                   QCOW2_OL_ACTIVE_L2);
+                    }
+                }
             }
             ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits,
                                      &refcount);
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 05e814d..7add805f 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -560,6 +560,13 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char 
*snapshot_id)
     g_free(sn_l1_table);
     sn_l1_table = NULL;
 
+    for (i = 0; i < s->l1_size; i++) {
+        uint64_t l2_offset = s->l1_table[i] & L1E_OFFSET_MASK;
+        if (l2_offset) {
+            qcow2_metadata_list_enter(bs, l2_offset, 1, QCOW2_OL_ACTIVE_L2);
+        }
+    }
+
     /*
      * Update QCOW_OFLAG_COPIED in the active L1 table (it may have changed
      * when we decreased the refcount of the old snapshot.
@@ -724,6 +731,13 @@ int qcow2_snapshot_load_tmp(BlockDriverState *bs,
                                                    sizeof(uint64_t)),
                                QCOW2_OL_ACTIVE_L1);
 
+    for (i = 0; i < s->l1_size; i++) {
+        uint64_t l2_offset = s->l1_table[i] & L1E_OFFSET_MASK;
+        if (l2_offset) {
+            qcow2_metadata_list_remove(bs, l2_offset, 1, QCOW2_OL_ACTIVE_L2);
+        }
+    }
+
     /* Switch the L1 table */
     qemu_vfree(s->l1_table);
 
@@ -740,5 +754,12 @@ int qcow2_snapshot_load_tmp(BlockDriverState *bs,
                                                   sizeof(uint64_t)),
                               QCOW2_OL_ACTIVE_L1);
 
+    for (i = 0; i < s->l1_size; i++) {
+        uint64_t l2_offset = s->l1_table[i] & L1E_OFFSET_MASK;
+        if (l2_offset) {
+            qcow2_metadata_list_enter(bs, l2_offset, 1, QCOW2_OL_ACTIVE_L2);
+        }
+    }
+
     return 0;
 }
diff --git a/block/qcow2.c b/block/qcow2.c
index c186452..b7d0f33 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -863,8 +863,14 @@ static int qcow2_open(BlockDriverState *bs, QDict 
*options, int flags,
             error_setg_errno(errp, -ret, "Could not read L1 table");
             goto fail;
         }
-        for(i = 0;i < s->l1_size; i++) {
+        for (i = 0; i < s->l1_size; i++) {
+            uint64_t l2_offset;
+
             be64_to_cpus(&s->l1_table[i]);
+            l2_offset = s->l1_table[i] & L1E_OFFSET_MASK;
+            if (l2_offset) {
+                qcow2_metadata_list_enter(bs, l2_offset, 1, 
QCOW2_OL_ACTIVE_L2);
+            }
         }
     }
 
-- 
2.4.6