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