On 10/30/2014 12:43 PM, Peter Lieven wrote:
> On 30.10.2014 12:23, Fam Zheng wrote:
>> Before, when a write protected iSCSI target is attached as scsi-disk
>> with BDRV_O_RDWR, we report it as writable, while in fact all writes
>> will fail.
>>
>> One way to improve this is to report write protect flag as true to
>> guest, but a even better way is to refuse using a write protected LUN to
>> guest.
>>
>> Target write protect flag is checked with a mode sense query.
>>
>> Signed-off-by: Fam Zheng <f...@redhat.com>
>> ---
>> v2: Improve error message.
>> Fall back to a warning if mode sense failed.
>> Check unmarshal return value.
>> ---
>> block/iscsi.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 46 insertions(+)
>>
>> diff --git a/block/iscsi.c b/block/iscsi.c
>> index 233f462..dcacbca 100644
>> --- a/block/iscsi.c
>> +++ b/block/iscsi.c
>> @@ -1219,6 +1219,44 @@ static void
>> iscsi_attach_aio_context(BlockDriverState *bs,
>> qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + NOP_INTERVAL);
>> }
>> +static bool iscsi_is_write_protected(IscsiLun *iscsilun)
>> +{
>> + struct scsi_task *task;
>> + struct scsi_mode_sense *ms = NULL;
>> +
>> + task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun,
>> + 1, SCSI_MODESENSE_PC_CURRENT,
>> + 0x3F,
>> + 0, 255);
>> +
>> + if (task == NULL) {
>> + error_report("Failed to send MODE_SENSE6 command: %s",
>> + iscsi_get_error(iscsilun->iscsi));
>> + goto out;
>> + }
>> +
>> + if (task->status != SCSI_STATUS_GOOD) {
>> + error_report("MODE_SENSE6 failed: %s",
>> + iscsi_get_error(iscsilun->iscsi));
>> + goto out;
>> + }
>> + ms = scsi_datain_unmarshall(task);
>> + if (!ms) {
>> + error_report("MODE_SENSE6 failed: %s",
>> + iscsi_get_error(iscsilun->iscsi));
>> + goto out;
>> + }
>> +out:
>> + if (task) {
>> + scsi_free_scsi_task(task);
>> + }
>> + if (!ms) {
>
> ms points to freed memory after scsi_free_scsi_task.
> furthermore the requests likely fails with task->status != SCSI_STATUS_GOOD
> if the modesense implementation is broken etc.
This is a mix of your and Fam's code. Looks good?
static bool iscsi_is_write_protected(IscsiLun *iscsilun)
{
struct scsi_task *task;
struct scsi_mode_sense *ms = NULL;
bool wrprotected = false;
task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun,
1, SCSI_MODESENSE_PC_CURRENT,
0x3F, 0, 255);
if (task == NULL) {
error_report("Failed to send MODE_SENSE(6) command: %s",
iscsi_get_error(iscsilun->iscsi));
goto out;
}
if (task->status != SCSI_STATUS_GOOD) {
error_report("MODE_SENSE(6) failed: %s",
iscsi_get_error(iscsilun->iscsi));
goto out;
}
ms = scsi_datain_unmarshall(task);
if (!ms) {
error_report("Failed to unmarshall MODE_SENSE(6) data: %s",
iscsi_get_error(iscsilun->iscsi));
goto out;
}
wrprotected = ms->device_specific_parameter & 0x80;
out:
if (task) {
scsi_free_scsi_task(task);
}
return wrprotected;
}
Paolo
