[Qemu-devel] [PATCH 08/12] 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 131e5b2..b749941 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -288,6 +288,8 @@ 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 1d76652..6cf73e9 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1043,6 +1043,12 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
             if (addend != 0) {
                 refcount = qcow2_update_cluster_refcount(bs, l2_offset >>
                         s->cluster_bits, addend, QCOW2_DISCARD_SNAPSHOT);
+                if (addend < 0) {
+                    if (l1_allocated) {
+                        qcow2_metadata_list_remove(bs, l2_offset, 1,
+                                                   QCOW2_OL_ACTIVE_L2);
+                    }
+                }
             } else {
                 refcount = qcow2_get_refcount(bs, l2_offset >> 
s->cluster_bits);
             }
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 41ea053..d83a939 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -561,6 +561,13 @@ 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.
@@ -725,6 +732,13 @@ 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);
 
@@ -741,5 +755,12 @@ 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 775cb39..d0950fc 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -850,8 +850,14 @@ 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);
+            }
         }
     }
 
-- 
1.9.3