Re: [Qemu-devel] [PATCH] iscsi: Refuse to open as writable if the LUN is write protected

[Peter Lieven]

Am 29.10.2014 um 14:31 schrieb Paolo Bonzini:
>
> On 10/29/2014 02:13 PM, 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 <address@hidden>
>> ---
>>  block/iscsi.c | 30 ++++++++++++++++++++++++++++++
>>  1 file changed, 30 insertions(+)
>>
>> diff --git a/block/iscsi.c b/block/iscsi.c
>> index 233f462..c154928 100644
>> --- a/block/iscsi.c
>> +++ b/block/iscsi.c
>> @@ -1339,6 +1339,36 @@ static int iscsi_open(BlockDriverState *bs, QDict 
>> *options, int flags,
>>      scsi_free_scsi_task(task);
>>      task = NULL;
>>  
>> +    /* Check the write protect flag of the LUN if we want to write */
>> +    if (flags & BDRV_O_RDWR) {
>> +        struct scsi_mode_sense *ms;
>> +
>> +        task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun,
>> +                                      1, SCSI_MODESENSE_PC_CURRENT,
>> +                                      0x3F,
>> +                                      0, 255);
>> +
>> +        if (task == NULL) {
>> +            error_setg(errp, "Failed to send MODE_SENSE10 command: %s\n",
> This is MODE SENSE(6).  Fixed and applied.
>
> Paolo
>
>> +                       iscsi_get_error(iscsilun->iscsi));
>> +            ret = -EINVAL;
>> +            goto out;
>> +        }
>> +
>> +        if (task->status != SCSI_STATUS_GOOD) {
>> +            error_setg(errp, "MODE_SENSE10 failed: %s\n",
>> +                       iscsi_get_error(iscsi));
>> +            ret = -EINVAL;
>> +            goto out;
>> +        }
>> +        ms = scsi_datain_unmarshall(task);

scsi_datain_unmarshall may fail. You need to check for NULL here.

Peter

>> +        if (ms->device_specific_parameter & 0x80) {
>> +            error_setg(errp, "Cannot open a write protected LUN as 
>> read-write");
>> +            ret = -EPERM;
>> +            goto out;
>> +        }
>> +    }
>> +
>>      iscsi_readcapacity_sync(iscsilun, &local_err);
>>      if (local_err != NULL) {
>>          error_propagate(errp, local_err);
>>