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scsi: ibmvscsi: Fix potential race after loss of transport 

After a loss of transport due to an adapter migration or crash/disconnect
from the host partner there is a tiny window where we can race adjusting
the request_limit of the adapter. The request limit is atomically
increased/decreased to track the number of inflight requests against the
allowed limit of our VIOS partner.

After a transport loss we set the request_limit to zero to reflect this
state.  However, there is a window where the adapter may attempt to queue a
command because the transport loss event hasn't been fully processed yet
and request_limit is still greater than zero.  The hypercall to send the
event will fail and the error path will increment the request_limit as a
result.  If the adapter processes the transport event prior to this
increment the request_limit becomes out of sync with the adapter state and
can result in SCSI commands being submitted on the now reset connection
prior to an SRP Login resulting in a protocol violation.

Fix this race by protecting request_limit with the host lock when changing
the value via atomic_set() to indicate no transport.

Link: https://lore.kernel.org/r/20201025001355.4527-1-tyreld@linux.ibm.com
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Tyrel Datwyler 2020-10-24 19:13:55 -05:00 committed by Martin K. Petersen
parent 2f4843b172
commit 665e0224a3
1 changed files with 26 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
drivers/scsi/ibmvscsi/ibmvscsi.c
View File

@ -806,6 +806,22 @@ static void purge_requests(struct ibmvscsi_host_data *hostdata, int error_code)
spin_unlock_irqrestore(hostdata->host->host_lock, flags);
}
/**
* ibmvscsi_set_request_limit - Set the adapter request_limit in response to
* an adapter failure, reset, or SRP Login. Done under host lock to prevent
* race with SCSI command submission.
* @hostdata: adapter to adjust
* @limit: new request limit
*/
static void ibmvscsi_set_request_limit(struct ibmvscsi_host_data *hostdata, int limit)
{
unsigned long flags;
spin_lock_irqsave(hostdata->host->host_lock, flags);
atomic_set(&hostdata->request_limit, limit);
spin_unlock_irqrestore(hostdata->host->host_lock, flags);
}
/**
* ibmvscsi_reset_host - Reset the connection to the server
* @hostdata: struct ibmvscsi_host_data to reset
@ -813,7 +829,7 @@ static void purge_requests(struct ibmvscsi_host_data *hostdata, int error_code)
static void ibmvscsi_reset_host(struct ibmvscsi_host_data *hostdata)
{
scsi_block_requests(hostdata->host);
atomic_set(&hostdata->request_limit, 0);
ibmvscsi_set_request_limit(hostdata, 0);
purge_requests(hostdata, DID_ERROR);
hostdata->action = IBMVSCSI_HOST_ACTION_RESET;
@ -1146,13 +1162,13 @@ static void login_rsp(struct srp_event_struct *evt_struct)
dev_info(hostdata->dev, "SRP_LOGIN_REJ reason %u\n",
evt_struct->xfer_iu->srp.login_rej.reason);
/* Login failed. */
atomic_set(&hostdata->request_limit, -1);
ibmvscsi_set_request_limit(hostdata, -1);
return;
default:
dev_err(hostdata->dev, "Invalid login response typecode 0x%02x!\n",
evt_struct->xfer_iu->srp.login_rsp.opcode);
/* Login failed. */
atomic_set(&hostdata->request_limit, -1);
ibmvscsi_set_request_limit(hostdata, -1);
return;
}
@ -1163,7 +1179,7 @@ static void login_rsp(struct srp_event_struct *evt_struct)
* This value is set rather than added to request_limit because
* request_limit could have been set to -1 by this client.
*/
atomic_set(&hostdata->request_limit,
ibmvscsi_set_request_limit(hostdata,
be32_to_cpu(evt_struct->xfer_iu->srp.login_rsp.req_lim_delta));
/* If we had any pending I/Os, kick them */
@ -1195,13 +1211,13 @@ static int send_srp_login(struct ibmvscsi_host_data *hostdata)
login->req_buf_fmt = cpu_to_be16(SRP_BUF_FORMAT_DIRECT |
SRP_BUF_FORMAT_INDIRECT);
spin_lock_irqsave(hostdata->host->host_lock, flags);
/* Start out with a request limit of 0, since this is negotiated in
* the login request we are just sending and login requests always
* get sent by the driver regardless of request_limit.
*/
atomic_set(&hostdata->request_limit, 0);
ibmvscsi_set_request_limit(hostdata, 0);
spin_lock_irqsave(hostdata->host->host_lock, flags);
rc = ibmvscsi_send_srp_event(evt_struct, hostdata, login_timeout * 2);
spin_unlock_irqrestore(hostdata->host->host_lock, flags);
dev_info(hostdata->dev, "sent SRP login\n");
@ -1781,7 +1797,7 @@ static void ibmvscsi_handle_crq(struct viosrp_crq *crq,
return;
case VIOSRP_CRQ_XPORT_EVENT: /* Hypervisor telling us the connection is closed */
scsi_block_requests(hostdata->host);
atomic_set(&hostdata->request_limit, 0);
ibmvscsi_set_request_limit(hostdata, 0);
if (crq->format == 0x06) {
/* We need to re-setup the interpartition connection */
dev_info(hostdata->dev, "Re-enabling adapter!\n");
@ -2137,12 +2153,12 @@ static void ibmvscsi_do_work(struct ibmvscsi_host_data *hostdata)
}
hostdata->action = IBMVSCSI_HOST_ACTION_NONE;
spin_unlock_irqrestore(hostdata->host->host_lock, flags);
if (rc) {
atomic_set(&hostdata->request_limit, -1);
ibmvscsi_set_request_limit(hostdata, -1);
dev_err(hostdata->dev, "error after %s\n", action);
}
spin_unlock_irqrestore(hostdata->host->host_lock, flags);
scsi_unblock_requests(hostdata->host);
}
@ -2226,7 +2242,7 @@ static int ibmvscsi_probe(struct vio_dev *vdev, const struct vio_device_id *id)
init_waitqueue_head(&hostdata->work_wait_q);
hostdata->host = host;
hostdata->dev = dev;
atomic_set(&hostdata->request_limit, -1);
ibmvscsi_set_request_limit(hostdata, -1);
hostdata->host->max_sectors = IBMVSCSI_MAX_SECTORS_DEFAULT;
if (map_persist_bufs(hostdata)) {