IB/srp: Fix a race condition between failing I/O and I/O completion

Avoid that srp_terminate_io() can access req->scmnd after it has been
cleared by the I/O completion code. Do this by protecting req->scmnd
accesses from srp_terminate_io() via locking

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 22 insertions, 11 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index a64e469db116..66a908bf3fb9 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -783,6 +783,7 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
  * srp_claim_req - Take ownership of the scmnd associated with a request.
  * @target: SRP target port.
  * @req: SRP request.
+ * @sdev: If not NULL, only take ownership for this SCSI device.
  * @scmnd: If NULL, take ownership of @req->scmnd. If not NULL, only take
  *         ownership of @req->scmnd if it equals @scmnd.
  *
@@ -791,16 +792,17 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
  */
 static struct scsi_cmnd *srp_claim_req(struct srp_target_port *target,
                                        struct srp_request *req,
+                                       struct scsi_device *sdev,
                                        struct scsi_cmnd *scmnd)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&target->lock, flags);
-        if (!scmnd) {
+        if (req->scmnd &&
+            (!sdev || req->scmnd->device == sdev) &&
+            (!scmnd || req->scmnd == scmnd)) {
                 scmnd = req->scmnd;
                 req->scmnd = NULL;
-        } else if (req->scmnd == scmnd) {
-                req->scmnd = NULL;
         } else {
                 scmnd = NULL;
         }
@@ -827,9 +829,10 @@ static void srp_free_req(struct srp_target_port *target,
 }
 
 static void srp_finish_req(struct srp_target_port *target,
-                           struct srp_request *req, int result)
+                           struct srp_request *req, struct scsi_device *sdev,
+                           int result)
 {
-        struct scsi_cmnd *scmnd = srp_claim_req(target, req, NULL);
+        struct scsi_cmnd *scmnd = srp_claim_req(target, req, sdev, NULL);
 
         if (scmnd) {
                 srp_free_req(target, req, scmnd, 0);
@@ -841,11 +844,20 @@ static void srp_finish_req(struct srp_target_port *target,
 static void srp_terminate_io(struct srp_rport *rport)
 {
         struct srp_target_port *target = rport->lld_data;
+        struct Scsi_Host *shost = target->scsi_host;
+        struct scsi_device *sdev;
         int i;
 
+        /*
+         * Invoking srp_terminate_io() while srp_queuecommand() is running
+         * is not safe. Hence the warning statement below.
+         */
+        shost_for_each_device(sdev, shost)
+                WARN_ON_ONCE(sdev->request_queue->request_fn_active);
+
         for (i = 0; i < target->req_ring_size; ++i) {
                 struct srp_request *req = &target->req_ring[i];
-                srp_finish_req(target, req, DID_TRANSPORT_FAILFAST << 16);
+                srp_finish_req(target, req, NULL, DID_TRANSPORT_FAILFAST << 16);
         }
 }
 
@@ -882,7 +894,7 @@ static int srp_rport_reconnect(struct srp_rport *rport)
 
         for (i = 0; i < target->req_ring_size; ++i) {
                 struct srp_request *req = &target->req_ring[i];
-                srp_finish_req(target, req, DID_RESET << 16);
+                srp_finish_req(target, req, NULL, DID_RESET << 16);
         }
 
         INIT_LIST_HEAD(&target->free_tx);
@@ -1290,7 +1302,7 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
                 complete(&target->tsk_mgmt_done);
         } else {
                 req = &target->req_ring[rsp->tag];
-                scmnd = srp_claim_req(target, req, NULL);
+                scmnd = srp_claim_req(target, req, NULL, NULL);
                 if (!scmnd) {
                         shost_printk(KERN_ERR, target->scsi_host,
                                      "Null scmnd for RSP w/tag %016llx\n",
@@ -2008,7 +2020,7 @@ static int srp_abort(struct scsi_cmnd *scmnd)
 
         shost_printk(KERN_ERR, target->scsi_host, "SRP abort called\n");
 
-        if (!req || !srp_claim_req(target, req, scmnd))
+        if (!req || !srp_claim_req(target, req, NULL, scmnd))
                 return SUCCESS;
         if (srp_send_tsk_mgmt(target, req->index, scmnd->device->lun,
                               SRP_TSK_ABORT_TASK) == 0)
@@ -2039,8 +2051,7 @@ static int srp_reset_device(struct scsi_cmnd *scmnd)
 
         for (i = 0; i < target->req_ring_size; ++i) {
                 struct srp_request *req = &target->req_ring[i];
-                if (req->scmnd && req->scmnd->device == scmnd->device)
-                        srp_finish_req(target, req, DID_RESET << 16);
+                srp_finish_req(target, req, scmnd->device, DID_RESET << 16);
         }
 
         return SUCCESS;