[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-block] [PATCH v2 2/7] block/qcow2-refcount: avoid eating RAM
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [PATCH v2 2/7] block/qcow2-refcount: avoid eating RAM |
Date: |
Mon, 8 Oct 2018 17:31:04 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 |
On 17.08.18 14:22, Vladimir Sementsov-Ogievskiy wrote:
> qcow2_inc_refcounts_imrt() (through realloc_refcount_array()) can eat
> an unpredictable amount of memory on corrupted table entries, which are
> referencing regions far beyond the end of file.
>
> Prevent this, by skipping such regions from further processing.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> block/qcow2-refcount.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index 615847eb09..566c19fbfa 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -1499,12 +1499,26 @@ int qcow2_inc_refcounts_imrt(BlockDriverState *bs,
> BdrvCheckResult *res,
> {
> BDRVQcow2State *s = bs->opaque;
> uint64_t start, last, cluster_offset, k, refcount;
> + int64_t file_len;
> int ret;
>
> if (size <= 0) {
> return 0;
> }
>
> + file_len = bdrv_getlength(bs->file->bs);
> + if (file_len < 0) {
> + return file_len;
> + }
Doesn't this slow things down? Can we not cache the length somewhere
and update it whenever the image is modified?
> +
> + if (offset + size - file_len > s->cluster_size) {
> + fprintf(stderr, "ERROR: counting reference for region exceeding the "
> + "end of the file by more than one cluster: offset 0x%" PRIx64
> + " size 0x%" PRIx64 "\n", offset, size);
Why is one cluster OK? Is there a specific case you're trying to catch
here?
Max
> + res->corruptions++;
> + return 0;
> + }
> +
> start = start_of_cluster(s, offset);
> last = start_of_cluster(s, offset + size - 1);
> for(cluster_offset = start; cluster_offset <= last;
>
signature.asc
Description: OpenPGP digital signature
- Re: [Qemu-block] [PATCH v2 2/7] block/qcow2-refcount: avoid eating RAM,
Max Reitz <=