[PATCH 02/17] qemuSnapshotRedefine: Fix use of snapshot definition after free

Peter Krempa pkrempa at redhat.com
Wed Jan 12 18:10:02 UTC 2022

Commit f4aae9726df factored out the snapshot redefinition code into a
separate function, but didn't account for the fact that the code is
consuming the reference to the snapshot definition and by moving the
code away the caller (qemuSnapshotCreateXML) now frees the definition
which didn't happen before as we cleared the pointer.

Fix it by increasing the reference locally. Later patches will refactor
the code so that it's more obvious what's happening.

Fixes: f4aae9726df
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2039651
Signed-off-by: Peter Krempa <pkrempa at redhat.com>
 src/qemu/qemu_snapshot.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_snapshot.c b/src/qemu/qemu_snapshot.c
index 624ace0314..f92e00f9c0 100644
--- a/src/qemu/qemu_snapshot.c
+++ b/src/qemu/qemu_snapshot.c
@@ -1709,13 +1709,14 @@ qemuSnapshotCreateWriteMetadata(virDomainObj *vm,
 static virDomainSnapshotPtr
 qemuSnapshotRedefine(virDomainObj *vm,
                      virDomainPtr domain,
-                     virDomainSnapshotDef *snapdef,
+                     virDomainSnapshotDef *snapdeftmp,
                      virQEMUDriver *driver,
                      virQEMUDriverConfig *cfg,
                      unsigned int flags)
     virDomainMomentObj *snap = NULL;
     virDomainSnapshotPtr ret = NULL;
+    g_autoptr(virDomainSnapshotDef) snapdef = virObjectRef(snapdeftmp);

     if (virDomainSnapshotRedefinePrep(vm, &snapdef, &snap,
@@ -1725,6 +1726,7 @@ qemuSnapshotRedefine(virDomainObj *vm,
     if (!snap) {
         if (!(snap = virDomainSnapshotAssignDef(vm->snapshots, snapdef)))
             return NULL;
+        snapdef = NULL;
     /* XXX Should we validate that the redefined snapshot even
      * makes sense, such as checking that qemu-img recognizes the

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