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Re: [PATCH v2 1/8] parallels: Out of image offset in BAT leads to image

From: Denis V. Lunev
Subject: Re: [PATCH v2 1/8] parallels: Out of image offset in BAT leads to image inflation
Date: Fri, 12 Aug 2022 16:13:45 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0

On 11.08.2022 17:00, Alexander Ivanov wrote:
When an image is opened, data_end field in BDRVParallelsState
is setted as the biggest offset in the BAT plus cluster size.
If there is a corrupted offset pointing outside the image,
the image size increase accordingly. It potentially leads
to attempts to create a file size of petabytes.

Set the data_end field with the original file size if the image
was opened for checking and repairing purposes or raise an error.

v2: No changes.
Changelog should be below ---
In that case it will not be merged.

There are a lot of typos/mistakes inside, I'd better use the comment

"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 and should be fixed."

With this change:
Reviewed-by: Denis V. Lunev <den@openvz.org>

Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
  block/parallels.c | 17 +++++++++++++++++
  1 file changed, 17 insertions(+)

diff --git a/block/parallels.c b/block/parallels.c
index a229c06f25..a76cf9d993 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -732,6 +732,7 @@ static int parallels_open(BlockDriverState *bs, QDict 
*options, int flags,
      BDRVParallelsState *s = bs->opaque;
      ParallelsHeader ph;
      int ret, size, i;
+    int64_t file_size;
      QemuOpts *opts = NULL;
      Error *local_err = NULL;
      char *buf;
@@ -811,6 +812,22 @@ static int parallels_open(BlockDriverState *bs, QDict 
*options, int flags,
+ file_size = bdrv_getlength(bs->file->bs);
+    if (file_size < 0) {
+        goto fail;
+    }
+    file_size >>= BDRV_SECTOR_BITS;
+    if (s->data_end > file_size) {
+        if (flags & BDRV_O_CHECK) {
+            s->data_end = file_size;
+        } else {
+            error_setg(errp, "parallels: Offset in BAT is out of image");
+            ret = -EINVAL;
+            goto fail;
+        }
+    }
      if (le32_to_cpu(ph.inuse) == HEADER_INUSE_MAGIC) {
          /* Image was not closed correctly. The check is mandatory */
          s->header_unclean = true;

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