qcow2: Fix error path for unknown incompatible features

qcow2's report_unsupported_feature() had two bugs: A 32 bit truncation
would prevent feature table entries for bits 32-63 from being used, and
it could assign errp multiple times if there was more than one unknown
feature, resulting in an error_set() assertion failure.

Fix the truncation, make sure to set the error exactly once and add a
qemu-iotests case for it.

This fixes https://bugs.launchpad.net/qemu/+bug/1342704/

Reported-by: Maria Kustova <maria.k@catit.be>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 16 insertions, 5 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index b0faa6917b..e1631d5086 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -210,20 +210,31 @@ static void GCC_FMT_ATTR(3, 4) report_unsupported(BlockDriverState *bs,
 static void report_unsupported_feature(BlockDriverState *bs,
     Error **errp, Qcow2Feature *table, uint64_t mask)
 {
+    char *features = g_strdup("");
+    char *old;
+
     while (table && table->name[0] != '\0') {
         if (table->type == QCOW2_FEAT_TYPE_INCOMPATIBLE) {
-            if (mask & (1 << table->bit)) {
-                report_unsupported(bs, errp, "%.46s", table->name);
-                mask &= ~(1 << table->bit);
+            if (mask & (1ULL << table->bit)) {
+                old = features;
+                features = g_strdup_printf("%s%s%.46s", old, *old ? ", " : "",
+                                           table->name);
+                g_free(old);
+                mask &= ~(1ULL << table->bit);
             }
         }
         table++;
     }
 
     if (mask) {
-        report_unsupported(bs, errp, "Unknown incompatible feature: %" PRIx64,
-                           mask);
+        old = features;
+        features = g_strdup_printf("%s%sUnknown incompatible feature: %" PRIx64,
+                                   old, *old ? ", " : "", mask);
+        g_free(old);
     }
+
+    report_unsupported(bs, errp, "%s", features);
+    g_free(features);
 }
 
 /*