parallels: Out of image offset in BAT leads to image inflation

data_end field in BDRVParallelsState is set to the biggest offset present
in BAT. If this offset is outside of the image, any further write will
create the cluster at this offset and/or the image will be truncated to
this offset on close. This is definitely not correct.

Raise an error in parallels_open() if data_end points outside the image
and it is not a check (let the check to repaire the image). Set data_end
to the end of the cluster with the last correct offset.

Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
Message-Id: <20230424093147.197643-2-alexander.ivanov@virtuozzo.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>

block/parallels.c

@@ -733,6 +733,7 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
     BDRVParallelsState *s = bs->opaque;
     ParallelsHeader ph;
     int ret, size, i;
+    int64_t file_nb_sectors;
     QemuOpts *opts = NULL;
     Error *local_err = NULL;
     char *buf;
@@ -742,6 +743,11 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
         return ret;
     }
 
+    file_nb_sectors = bdrv_nb_sectors(bs->file->bs);
+    if (file_nb_sectors < 0) {
+        return -EINVAL;
+    }
+
     ret = bdrv_pread(bs->file, 0, sizeof(ph), &ph, 0);
     if (ret < 0) {
         goto fail;
@@ -806,6 +812,17 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
 
     for (i = 0; i < s->bat_size; i++) {
         int64_t off = bat2sect(s, i);
+        if (off >= file_nb_sectors) {
+            if (flags & BDRV_O_CHECK) {
+                continue;
+            }
+            error_setg(errp, "parallels: Offset %" PRIi64 " in BAT[%d] entry "
+                       "is larger than file size (%" PRIi64 ")",
+                       off << BDRV_SECTOR_BITS, i,
+                       file_nb_sectors << BDRV_SECTOR_BITS);
+            ret = -EINVAL;
+            goto fail;
+        }
         if (off >= s->data_end) {
             s->data_end = off + s->tracks;
         }