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block: Fail gracefully when blockdev-snapshot creates loops 

Using blockdev-snapshot to append a node as an overlay to itself, or to
any of its parents, causes crashes. Catch the condition and return an
error for these cases instead.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1824363
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211018134714.48438-1-kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2021-10-18 15:47:14 +02:00
parent 13a028336f
commit bfb8aa6d58
3 changed files with 70 additions and 4 deletions
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10
block.c
View File

@ -84,6 +84,9 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
BdrvChildRole child_role,
Error **errp);
static bool bdrv_recurse_has_child(BlockDriverState *bs,
BlockDriverState *child);
static void bdrv_replace_child_noperm(BdrvChild *child,
BlockDriverState *new_bs);
static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
@ -2673,6 +2676,7 @@ static void bdrv_replace_child_noperm(BdrvChild *child,
int drain_saldo;
assert(!child->frozen);
assert(old_bs != new_bs);
if (old_bs && new_bs) {
assert(bdrv_get_aio_context(old_bs) == bdrv_get_aio_context(new_bs));
@ -2892,6 +2896,12 @@ static int bdrv_attach_child_noperm(BlockDriverState *parent_bs,
assert(parent_bs->drv);
if (bdrv_recurse_has_child(child_bs, parent_bs)) {
error_setg(errp, "Making '%s' a %s child of '%s' would create a cycle",
child_bs->node_name, child_name, parent_bs->node_name);
return -EINVAL;
}
bdrv_get_cumulative_perm(parent_bs, &perm, &shared_perm);
bdrv_child_perm(parent_bs, child_bs, NULL, child_role, NULL,
perm, shared_perm, &perm, &shared_perm);

31
tests/qemu-iotests/085
View File

@ -103,11 +103,18 @@ do_blockdev_add()
}
# ${1}: unique identifier for the snapshot filename
add_snapshot_image()
create_snapshot_image()
{
base_image="${TEST_DIR}/$((${1}-1))-${snapshot_virt0}"
snapshot_file="${TEST_DIR}/${1}-${snapshot_virt0}"
TEST_IMG=$snapshot_file _make_test_img -u -b "${base_image}" -F $IMGFMT "$size"
}
# ${1}: unique identifier for the snapshot filename
add_snapshot_image()
{
snapshot_file="${TEST_DIR}/${1}-${snapshot_virt0}"
create_snapshot_image "$1"
do_blockdev_add "$1" "'backing': null, " "${snapshot_file}"
}
@ -230,6 +237,28 @@ _make_test_img -b "${TEST_IMG}.base" -F $IMGFMT "$size"
do_blockdev_add ${SNAPSHOTS} "" "${TEST_IMG}"
blockdev_snapshot ${SNAPSHOTS} error
echo
echo === Invalid command - creating loops ===
echo
SNAPSHOTS=$((${SNAPSHOTS}+1))
add_snapshot_image ${SNAPSHOTS}
_send_qemu_cmd $h "{ 'execute': 'blockdev-snapshot',
'arguments': { 'node':'snap_${SNAPSHOTS}',
'overlay':'snap_${SNAPSHOTS}' }
}" "error"
SNAPSHOTS=$((${SNAPSHOTS}+1))
create_snapshot_image ${SNAPSHOTS}
do_blockdev_add ${SNAPSHOTS} "'backing': 'snap_$((${SNAPSHOTS}-1))', " \
"${TEST_DIR}/${SNAPSHOTS}-${snapshot_virt0}"
_send_qemu_cmd $h "{ 'execute': 'blockdev-snapshot',
'arguments': { 'node':'snap_${SNAPSHOTS}',
'overlay':'snap_$((${SNAPSHOTS}-1))' }
}" "error"
echo
echo === Invalid command - The node does not exist ===
echo

33
tests/qemu-iotests/085.out
View File

@ -217,15 +217,42 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/
'overlay':'snap_13' } }
{"error": {"class": "GenericError", "desc": "The overlay already has a backing image"}}
=== Invalid command - creating loops ===
Formatting 'TEST_DIR/14-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/13-snapshot-v0.IMGFMT backing_fmt=IMGFMT
{ 'execute': 'blockdev-add', 'arguments':
{ 'driver': 'IMGFMT', 'node-name': 'snap_14', 'backing': null,
'file':
{ 'driver': 'file', 'filename': 'TEST_DIR/14-snapshot-v0.IMGFMT',
'node-name': 'file_14' } } }
{"return": {}}
{ 'execute': 'blockdev-snapshot',
'arguments': { 'node':'snap_14',
'overlay':'snap_14' }
}
{"error": {"class": "GenericError", "desc": "Making 'snap_14' a backing child of 'snap_14' would create a cycle"}}
Formatting 'TEST_DIR/15-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/14-snapshot-v0.IMGFMT backing_fmt=IMGFMT
{ 'execute': 'blockdev-add', 'arguments':
{ 'driver': 'IMGFMT', 'node-name': 'snap_15', 'backing': 'snap_14',
'file':
{ 'driver': 'file', 'filename': 'TEST_DIR/15-snapshot-v0.IMGFMT',
'node-name': 'file_15' } } }
{"return": {}}
{ 'execute': 'blockdev-snapshot',
'arguments': { 'node':'snap_15',
'overlay':'snap_14' }
}
{"error": {"class": "GenericError", "desc": "Making 'snap_15' a backing child of 'snap_14' would create a cycle"}}
=== Invalid command - The node does not exist ===
{ 'execute': 'blockdev-snapshot',
'arguments': { 'node': 'virtio0',
'overlay':'snap_14' } }
{"error": {"class": "GenericError", "desc": "Cannot find device='snap_14' nor node-name='snap_14'"}}
'overlay':'snap_16' } }
{"error": {"class": "GenericError", "desc": "Cannot find device='snap_16' nor node-name='snap_16'"}}
{ 'execute': 'blockdev-snapshot',
'arguments': { 'node':'nodevice',
'overlay':'snap_13' }
'overlay':'snap_15' }
}
{"error": {"class": "GenericError", "desc": "Cannot find device='nodevice' nor node-name='nodevice'"}}
*** done