IB/srp: Fix a sporadic crash triggered by cable pulling

Avoid that the loops that iterate over the request ring can encounter
a pointer to a SCSI command in req->scmnd that is no longer associated
with that request. If the function srp_unmap_data() is invoked twice
for a SCSI command that is not in flight then that would cause
ib_fmr_pool_unmap() to be invoked with an invalid pointer as argument,
resulting in a kernel oops.

Reported-by: Sagi Grimberg <sagig@mellanox.com>
Reference: http://thread.gmane.org/gmane.linux.drivers.rdma/19068/focus=19069
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Cc: stable <stable@vger.kernel.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 66a908bf3fb9e1d43654d07af1d346cca12a6223..5b2bed8fc4932c2f070af2b62677a4931751cdd7 100644 (file)
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -1594,6 +1594,12 @@ err_unmap:
 err_iu:
        srp_put_tx_iu(target, iu, SRP_IU_CMD);
 
+       /*
+        * Avoid that the loops that iterate over the request ring can
+        * encounter a dangling SCSI command pointer.
+        */
+       req->scmnd = NULL;
+
        spin_lock_irqsave(&target->lock, flags);
        list_add(&req->list, &target->free_reqs);