[Qemu-devel] [PATCH 2/3] migration: Check for ID length

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The qdev id of a device can be huge if it's on the end of a chain
of bridges; in reality such chains shouldn't occur but they can
be made to by chaining PCIe bridges together.

The migration format has a number of 256 character long format
limits; check we don't hit them (we already use pstrcat/cpy but
that just protects us from buffer overruns, we fairly quickly
hit an assert).

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 include/migration/vmstate.h |  2 ++
 migration/savevm.c          | 21 ++++++++++++++++-----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 73f3182..93b4722 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -949,12 +949,14 @@ void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
 
 bool vmstate_save_needed(const VMStateDescription *vmsd, void *opaque);
 
+/* Returns: 0 on success, -1 on failure */
 int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
                                    const VMStateDescription *vmsd,
                                    void *base, int alias_id,
                                    int required_for_version,
                                    Error **errp);
 
+/* Returns: 0 on success, -1 on failure */
 static inline int vmstate_register(DeviceState *dev, int instance_id,
                                    const VMStateDescription *vmsd,
                                    void *opaque)
diff --git a/migration/savevm.c b/migration/savevm.c
index ae3ab2c..84324b2 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -559,8 +559,14 @@ int register_savevm_live(DeviceState *dev,
     if (dev) {
         char *id = qdev_get_dev_path(dev);
         if (id) {
-            pstrcpy(se->idstr, sizeof(se->idstr), id);
-            pstrcat(se->idstr, sizeof(se->idstr), "/");
+            if (snprintf(se->idstr, sizeof(se->idstr), "%s/", id) >=
+                sizeof(se->idstr)) {
+                error_report("Path too long for VMState (%s)", id);
+                g_free(id);
+                g_free(se);
+
+                return -1;
+            }
             g_free(id);
 
             se->compat = g_new0(CompatEntry, 1);
@@ -644,9 +650,14 @@ int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
     if (dev) {
         char *id = qdev_get_dev_path(dev);
         if (id) {
-            pstrcpy(se->idstr, sizeof(se->idstr), id);
-            pstrcat(se->idstr, sizeof(se->idstr), "/");
-            g_free(id);
+            if (snprintf(se->idstr, sizeof(se->idstr), "%s/", id) >=
+                sizeof(se->idstr)) {
+                error_setg(errp, "Path too long for VMState (%s)", id);
+                g_free(id);
+                g_free(se);
+
+                return -1;
+            }
 
             se->compat = g_new0(CompatEntry, 1);
             pstrcpy(se->compat->idstr, sizeof(se->compat->idstr), vmsd->name);
-- 
2.9.3