scsi_transport_srp: Fix a race condition
The rport timers must be stopped before the SRP initiator destroys the
resources associated with the SCSI host. This is necessary because
otherwise the callback functions invoked from the SRP transport layer
could trigger a use-after-free. Stopping the rport timers before
invoking scsi_remove_host() can trigger long delays in the SCSI error
handler if a transport layer failure occurs while scsi_remove_host()
is in progress. Hence move the code for stopping the rport timers from
srp_rport_release() into a new function and invoke that function after
scsi_remove_host() has finished. This patch fixes the following
sporadic kernel crash:
kernel BUG at include/asm-generic/dma-mapping-common.h:64!
invalid opcode: 0000 [#1] SMP
RIP: 0010:[<ffffffffa03b20b1>] [<ffffffffa03b20b1>] srp_unmap_data+0x121/0x130 [ib_srp]
Call Trace:
[<ffffffffa03b20fc>] srp_free_req+0x3c/0x80 [ib_srp]
[<ffffffffa03b2188>] srp_finish_req+0x48/0x70 [ib_srp]
[<ffffffffa03b21fb>] srp_terminate_io+0x4b/0x60 [ib_srp]
[<ffffffffa03a6fb5>] __rport_fail_io_fast+0x75/0x80 [scsi_transport_srp]
[<ffffffffa03a7438>] rport_fast_io_fail_timedout+0x88/0xc0 [scsi_transport_srp]
[<ffffffff8108b370>] worker_thread+0x170/0x2a0
[<ffffffff81090876>] kthread+0x96/0xa0
[<ffffffff8100c0ca>] child_rip+0xa/0x20
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index a886319..529b6bc 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -660,6 +660,7 @@
srp_rport_get(target->rport);
srp_remove_host(target->scsi_host);
scsi_remove_host(target->scsi_host);
+ srp_stop_rport_timers(target->rport);
srp_disconnect_target(target);
ib_destroy_cm_id(target->cm_id);
srp_free_target_ib(target);
diff --git a/drivers/scsi/scsi_transport_srp.c b/drivers/scsi/scsi_transport_srp.c
index 8b9cb22..a349d44 100644
--- a/drivers/scsi/scsi_transport_srp.c
+++ b/drivers/scsi/scsi_transport_srp.c
@@ -456,37 +456,29 @@
lockdep_assert_held(&rport->mutex);
- if (!rport->deleted) {
- delay = rport->reconnect_delay;
- fast_io_fail_tmo = rport->fast_io_fail_tmo;
- dev_loss_tmo = rport->dev_loss_tmo;
- pr_debug("%s current state: %d\n",
- dev_name(&shost->shost_gendev), rport->state);
+ delay = rport->reconnect_delay;
+ fast_io_fail_tmo = rport->fast_io_fail_tmo;
+ dev_loss_tmo = rport->dev_loss_tmo;
+ pr_debug("%s current state: %d\n", dev_name(&shost->shost_gendev),
+ rport->state);
- if (delay > 0)
+ if (rport->state == SRP_RPORT_LOST)
+ return;
+ if (delay > 0)
+ queue_delayed_work(system_long_wq, &rport->reconnect_work,
+ 1UL * delay * HZ);
+ if (srp_rport_set_state(rport, SRP_RPORT_BLOCKED) == 0) {
+ pr_debug("%s new state: %d\n", dev_name(&shost->shost_gendev),
+ rport->state);
+ scsi_target_block(&shost->shost_gendev);
+ if (fast_io_fail_tmo >= 0)
queue_delayed_work(system_long_wq,
- &rport->reconnect_work,
- 1UL * delay * HZ);
- if (srp_rport_set_state(rport, SRP_RPORT_BLOCKED) == 0) {
- pr_debug("%s new state: %d\n",
- dev_name(&shost->shost_gendev),
- rport->state);
- scsi_target_block(&shost->shost_gendev);
- if (fast_io_fail_tmo >= 0)
- queue_delayed_work(system_long_wq,
- &rport->fast_io_fail_work,
- 1UL * fast_io_fail_tmo * HZ);
- if (dev_loss_tmo >= 0)
- queue_delayed_work(system_long_wq,
- &rport->dev_loss_work,
- 1UL * dev_loss_tmo * HZ);
- }
- } else {
- pr_debug("%s has already been deleted\n",
- dev_name(&shost->shost_gendev));
- srp_rport_set_state(rport, SRP_RPORT_FAIL_FAST);
- scsi_target_unblock(&shost->shost_gendev,
- SDEV_TRANSPORT_OFFLINE);
+ &rport->fast_io_fail_work,
+ 1UL * fast_io_fail_tmo * HZ);
+ if (dev_loss_tmo >= 0)
+ queue_delayed_work(system_long_wq,
+ &rport->dev_loss_work,
+ 1UL * dev_loss_tmo * HZ);
}
}
@@ -560,7 +552,7 @@
scsi_target_block(&shost->shost_gendev);
while (scsi_request_fn_active(shost))
msleep(20);
- res = i->f->reconnect(rport);
+ res = rport->state != SRP_RPORT_LOST ? i->f->reconnect(rport) : -ENODEV;
pr_debug("%s (state %d): transport.reconnect() returned %d\n",
dev_name(&shost->shost_gendev), rport->state, res);
if (res == 0) {
@@ -626,10 +618,6 @@
{
struct srp_rport *rport = dev_to_rport(dev);
- cancel_delayed_work_sync(&rport->reconnect_work);
- cancel_delayed_work_sync(&rport->fast_io_fail_work);
- cancel_delayed_work_sync(&rport->dev_loss_work);
-
put_device(dev->parent);
kfree(rport);
}
@@ -784,12 +772,6 @@
device_del(dev);
transport_destroy_device(dev);
- mutex_lock(&rport->mutex);
- if (rport->state == SRP_RPORT_BLOCKED)
- __rport_fail_io_fast(rport);
- rport->deleted = true;
- mutex_unlock(&rport->mutex);
-
put_device(dev);
}
EXPORT_SYMBOL_GPL(srp_rport_del);
@@ -814,6 +796,27 @@
}
EXPORT_SYMBOL_GPL(srp_remove_host);
+/**
+ * srp_stop_rport_timers - stop the transport layer recovery timers
+ *
+ * Must be called after srp_remove_host() and scsi_remove_host(). The caller
+ * must hold a reference on the rport (rport->dev) and on the SCSI host
+ * (rport->dev.parent).
+ */
+void srp_stop_rport_timers(struct srp_rport *rport)
+{
+ mutex_lock(&rport->mutex);
+ if (rport->state == SRP_RPORT_BLOCKED)
+ __rport_fail_io_fast(rport);
+ srp_rport_set_state(rport, SRP_RPORT_LOST);
+ mutex_unlock(&rport->mutex);
+
+ cancel_delayed_work_sync(&rport->reconnect_work);
+ cancel_delayed_work_sync(&rport->fast_io_fail_work);
+ cancel_delayed_work_sync(&rport->dev_loss_work);
+}
+EXPORT_SYMBOL_GPL(srp_stop_rport_timers);
+
static int srp_tsk_mgmt_response(struct Scsi_Host *shost, u64 nexus, u64 tm_id,
int result)
{
diff --git a/include/scsi/scsi_transport_srp.h b/include/scsi/scsi_transport_srp.h
index 4ebf691..f24e763 100644
--- a/include/scsi/scsi_transport_srp.h
+++ b/include/scsi/scsi_transport_srp.h
@@ -19,7 +19,7 @@
* @SRP_RPORT_BLOCKED: Transport layer not operational; fast I/O fail timer
* is running and I/O has been blocked.
* @SRP_RPORT_FAIL_FAST: Fast I/O fail timer has expired; fail I/O fast.
- * @SRP_RPORT_LOST: Device loss timer has expired; port is being removed.
+ * @SRP_RPORT_LOST: Port is being removed.
*/
enum srp_rport_state {
SRP_RPORT_RUNNING,
@@ -48,7 +48,6 @@
struct mutex mutex;
enum srp_rport_state state;
- bool deleted;
int reconnect_delay;
int failed_reconnects;
struct delayed_work reconnect_work;
@@ -101,6 +100,7 @@
extern int srp_reconnect_rport(struct srp_rport *rport);
extern void srp_start_tl_fail_timers(struct srp_rport *rport);
extern void srp_remove_host(struct Scsi_Host *);
+extern void srp_stop_rport_timers(struct srp_rport *rport);
/**
* srp_chkready() - evaluate the transport layer state before I/O