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Re: [Qemu-devel] [PATCH 4/4] qcow2: Check L1/L2/reftable entries for ali
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 4/4] qcow2: Check L1/L2/reftable entries for alignment |
Date: |
Wed, 20 Aug 2014 12:51:21 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 16.08.2014 um 23:16 hat Max Reitz geschrieben:
> Offsets taken from the L1, L2 and refcount tables are generally assumed
> to be correctly aligned. However, this cannot be guaranteed if the image
> has been written to by something different than qemu, thus check all
> offsets taken from these tables for correct cluster alignment.
>
> Signed-off-by: Max Reitz <address@hidden>
> ---
> block/qcow2-cluster.c | 27 ++++++++++++++++++++++++++-
> block/qcow2-refcount.c | 36 ++++++++++++++++++++++++++++++++++--
> 2 files changed, 60 insertions(+), 3 deletions(-)
Can you extend qemu-iotests 060 to check each of these cases?
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index 5b36018..2cc41b2 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -486,6 +486,12 @@ int qcow2_get_cluster_offset(BlockDriverState *bs,
> uint64_t offset,
> goto out;
> }
>
> + if (offset_into_cluster(s, l2_offset)) {
> + qcow2_signal_corruption(bs, -1, -1, "L2 table offset %#" PRIx64
> + " unaligned", l2_offset);
Should we include l1_index in the message? If you want to debug the
image with a hex editor or something, this is important information.
> + return -EIO;
> + }
> +
> /* load the l2 table in memory */
>
> ret = l2_load(bs, l2_offset, &l2_table);
> @@ -525,6 +531,12 @@ int qcow2_get_cluster_offset(BlockDriverState *bs,
> uint64_t offset,
> c = count_contiguous_clusters(nb_clusters, s->cluster_size,
> &l2_table[l2_index], QCOW_OFLAG_ZERO);
> *cluster_offset &= L2E_OFFSET_MASK;
> + if (offset_into_cluster(s, *cluster_offset)) {
> + qcow2_signal_corruption(bs, -1, -1, "Data cluster offset %#"
> PRIx64
> + " unaligned", *cluster_offset);
The same thing here would be offset.
> + qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
> + return -EIO;
> + }
I wonder whether a goto fail would start to make sense now, zero
clusters in v2 images have the same qcow2_cache_put/return -EIO code.
And actually, that's a corruption case as well, so we might call
qcow2_signal_corruption() there.
> break;
> default:
> abort();
> @@ -576,6 +588,11 @@ static int get_cluster_table(BlockDriverState *bs,
> uint64_t offset,
>
> assert(l1_index < s->l1_size);
> l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
> + if (offset_into_cluster(s, l2_offset)) {
> + qcow2_signal_corruption(bs, -1, -1, "L2 table offset %#" PRIx64
> + " unaligned", l2_offset);
l1_index again.
> + return -EIO;
> + }
>
> /* seek the l2 table of the given l2 offset */
>
> @@ -948,6 +965,14 @@ static int handle_copied(BlockDriverState *bs, uint64_t
> guest_offset,
> bool offset_matches =
> (cluster_offset & L2E_OFFSET_MASK) == *host_offset;
>
> + if (offset_into_cluster(s, cluster_offset & L2E_OFFSET_MASK)) {
> + qcow2_signal_corruption(bs, -1, -1, "Data cluster offset %#llx "
> + "unaligned",
> + cluster_offset & L2E_OFFSET_MASK);
Worth adding guest_offset.
> + ret = -EIO;
> + goto out;
> + }
> +
> if (*host_offset != 0 && !offset_matches) {
> *bytes = 0;
> ret = 0;
> @@ -979,7 +1004,7 @@ out:
>
> /* Only return a host offset if we actually made progress. Otherwise we
> * would make requirements for handle_alloc() that it can't fulfill */
> - if (ret) {
> + if (ret > 0) {
> *host_offset = (cluster_offset & L2E_OFFSET_MASK)
> + offset_into_cluster(s, guest_offset);
> }
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index 0ac1339..fac2963 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -108,6 +108,12 @@ static int get_refcount(BlockDriverState *bs, int64_t
> cluster_index)
> if (!refcount_block_offset)
> return 0;
>
> + if (offset_into_cluster(s, refcount_block_offset)) {
> + qcow2_signal_corruption(bs, -1, -1, "Refblock offset %#" PRIx64
> + " unaligned", refcount_block_offset);
Add refcount_table_index.
> + return -EIO;
> + }
> +
> ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset,
> (void**) &refcount_block);
> if (ret < 0) {
> @@ -181,6 +187,12 @@ static int alloc_refcount_block(BlockDriverState *bs,
>
> /* If it's already there, we're done */
> if (refcount_block_offset) {
> + if (offset_into_cluster(s, refcount_block_offset)) {
> + qcow2_signal_corruption(bs, -1, -1, "Refblock offset %#"
> PRIx64
> + " unaligned", refcount_block_offset);
> + return -EIO;
> + }
Same here.
> return load_refcount_block(bs, refcount_block_offset,
> (void**) refcount_block);
> }
> @@ -836,8 +848,13 @@ void qcow2_free_any_clusters(BlockDriverState *bs,
> uint64_t l2_entry,
> case QCOW2_CLUSTER_NORMAL:
> case QCOW2_CLUSTER_ZERO:
> if (l2_entry & L2E_OFFSET_MASK) {
> - qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK,
> - nb_clusters << s->cluster_bits, type);
> + if (offset_into_cluster(s, l2_entry & L2E_OFFSET_MASK)) {
> + fprintf(stderr, "qcow2: Cannot free unaligned cluster
> %#llx\n",
> + l2_entry & L2E_OFFSET_MASK);
> + } else {
> + qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK,
> + nb_clusters << s->cluster_bits, type);
> + }
Hm... Why isn't this a corruption like any other? Unconditional
fprintf() is something I don't like a lot.
> }
> break;
> case QCOW2_CLUSTER_UNALLOCATED:
> @@ -901,6 +918,13 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
> old_l2_offset = l2_offset;
> l2_offset &= L1E_OFFSET_MASK;
>
> + if (offset_into_cluster(s, l2_offset)) {
> + qcow2_signal_corruption(bs, -1, -1, "L2 table offset %#"
> PRIx64
> + " unaligned", l2_offset);
> + ret = -EIO;
> + goto fail;
> + }
Add the L1 index (i) to the message.
> ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
> (void**) &l2_table);
> if (ret < 0) {
> @@ -933,6 +957,14 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
>
> case QCOW2_CLUSTER_NORMAL:
> case QCOW2_CLUSTER_ZERO:
> + if (offset_into_cluster(s, offset &
> L2E_OFFSET_MASK)) {
> + qcow2_signal_corruption(bs, -1, -1, "Data
> cluster "
> + "offset %#llx unaligned",
> + offset &
> L2E_OFFSET_MASK);
We don't have a single index describing the cluster here, so you might
either just print both L1 and L2 index or calculate a cluster index. The
former is probably easier and even more useful.
> + ret = -EIO;
> + goto fail;
> + }
> +
> cluster_index = (offset & L2E_OFFSET_MASK) >>
> s->cluster_bits;
> if (!cluster_index) {
> /* unallocated */
Kevin
[Qemu-devel] [PATCH 3/4] iotests: Fix output of 060, Max Reitz, 2014/08/16