qemu-e2k/tests/qemu-iotests/058
Eric Blake 1104d83c72 nbd-client: Refuse read-only client with BDRV_O_RDWR
The NBD spec says that clients should not try to write/trim to
an export advertised as read-only by the server.  But we failed
to check that, and would allow the block layer to use NBD with
BDRV_O_RDWR even when the server is read-only, which meant we
were depending on the server sending a proper EPERM failure for
various commands, and also exposes a leaky abstraction: using
qemu-io in read-write mode would succeed on 'w -z 0 0' because
of local short-circuiting logic, but 'w 0 0' would send a
request over the wire (where it then depends on the server, and
fails at least for qemu-nbd but might pass for other NBD
implementations).

With this patch, a client MUST request read-only mode to access
a server that is doing a read-only export, or else it will get
a message like:

can't open device nbd://localhost:10809/foo: request for write access conflicts with read-only export

It is no longer possible to even attempt writes over the wire
(including the corner case of 0-length writes), because the block
layer enforces the explicit read-only request; this matches the
behavior of qcow2 when backed by a read-only POSIX file.

Fix several iotests to comply with the new behavior (since
qemu-nbd of an internal snapshot, as well as nbd-server-add over QMP,
default to a read-only export, we must tell blockdev-add/qemu-io to
set up a read-only client).

CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171108215703.9295-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
2017-11-09 10:10:17 -06:00

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#!/bin/bash
#
# Test export internal snapshot by qemu-nbd, convert it by qemu-img.
#
# Copyright (C) 2013 IBM, Inc.
#
# Based on 029.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# creator
owner=xiawenc@linux.vnet.ibm.com
seq=`basename $0`
echo "QA output created by $seq"
here=`pwd`
status=1 # failure is the default!
nbd_unix_socket=$TEST_DIR/test_qemu_nbd_socket
nbd_snapshot_img="nbd:unix:$nbd_unix_socket"
rm -f "${TEST_DIR}/qemu-nbd.pid"
_cleanup_nbd()
{
local NBD_SNAPSHOT_PID
if [ -f "${TEST_DIR}/qemu-nbd.pid" ]; then
read NBD_SNAPSHOT_PID < "${TEST_DIR}/qemu-nbd.pid"
rm -f "${TEST_DIR}/qemu-nbd.pid"
if [ -n "$NBD_SNAPSHOT_PID" ]; then
kill "$NBD_SNAPSHOT_PID"
fi
fi
rm -f "$nbd_unix_socket"
}
_wait_for_nbd()
{
for ((i = 0; i < 300; i++))
do
if [ -r "$nbd_unix_socket" ]; then
return
fi
sleep 0.1
done
echo "Failed in check of unix socket created by qemu-nbd"
exit 1
}
converted_image=$TEST_IMG.converted
_export_nbd_snapshot()
{
_cleanup_nbd
$QEMU_NBD -v -t -k "$nbd_unix_socket" "$TEST_IMG" -l $1 &
_wait_for_nbd
}
_export_nbd_snapshot1()
{
_cleanup_nbd
$QEMU_NBD -v -t -k "$nbd_unix_socket" "$TEST_IMG" -l snapshot.name=$1 &
_wait_for_nbd
}
_cleanup()
{
_cleanup_nbd
_cleanup_test_img
rm -f "$converted_image"
}
trap "_cleanup; exit \$status" 0 1 2 3 15
# get standard environment, filters and checks
. ./common.rc
. ./common.filter
. ./common.pattern
_supported_fmt qcow2
_supported_proto file
_supported_os Linux
_require_command QEMU_NBD
# Internal snapshots are (currently) impossible with refcount_bits=1
_unsupported_imgopts 'refcount_bits=1[^0-9]'
# Use -f raw instead of -f $IMGFMT for the NBD connection
QEMU_IO_NBD="$QEMU_IO -f raw --cache=$CACHEMODE"
echo
echo "== preparing image =="
_make_test_img 64M
$QEMU_IO -c 'write -P 0xa 0x1000 0x1000' "$TEST_IMG" | _filter_qemu_io
$QEMU_IO -c 'write -P 0xb 0x2000 0x1000' "$TEST_IMG" | _filter_qemu_io
$QEMU_IMG snapshot -c sn1 "$TEST_IMG"
$QEMU_IO -c 'write -P 0xc 0x1000 0x1000' "$TEST_IMG" | _filter_qemu_io
$QEMU_IO -c 'write -P 0xd 0x2000 0x1000' "$TEST_IMG" | _filter_qemu_io
_check_test_img
echo
echo "== verifying the image file with patterns =="
$QEMU_IO -c 'read -P 0xc 0x1000 0x1000' "$TEST_IMG" | _filter_qemu_io
$QEMU_IO -c 'read -P 0xd 0x2000 0x1000' "$TEST_IMG" | _filter_qemu_io
_export_nbd_snapshot sn1
echo
echo "== verifying the exported snapshot with patterns, method 1 =="
$QEMU_IO_NBD -r -c 'read -P 0xa 0x1000 0x1000' "$nbd_snapshot_img" | _filter_qemu_io
$QEMU_IO_NBD -r -c 'read -P 0xb 0x2000 0x1000' "$nbd_snapshot_img" | _filter_qemu_io
_export_nbd_snapshot1 sn1
echo
echo "== verifying the exported snapshot with patterns, method 2 =="
$QEMU_IO_NBD -r -c 'read -P 0xa 0x1000 0x1000' "$nbd_snapshot_img" | _filter_qemu_io
$QEMU_IO_NBD -r -c 'read -P 0xb 0x2000 0x1000' "$nbd_snapshot_img" | _filter_qemu_io
$QEMU_IMG convert "$TEST_IMG" -l sn1 -O qcow2 "$converted_image"
echo
echo "== verifying the converted snapshot with patterns, method 1 =="
$QEMU_IO -c 'read -P 0xa 0x1000 0x1000' "$converted_image" | _filter_qemu_io
$QEMU_IO -c 'read -P 0xb 0x2000 0x1000' "$converted_image" | _filter_qemu_io
$QEMU_IMG convert "$TEST_IMG" -l snapshot.name=sn1 -O qcow2 "$converted_image"
echo
echo "== verifying the converted snapshot with patterns, method 2 =="
$QEMU_IO -c 'read -P 0xa 0x1000 0x1000' "$converted_image" | _filter_qemu_io
$QEMU_IO -c 'read -P 0xb 0x2000 0x1000' "$converted_image" | _filter_qemu_io
# success, all done
echo "*** done"
rm -f $seq.full
status=0