NVMe: fix race condition in nvme_submit_sync_cmd()

If we have a race between the schedule timing out and the command
completing, we could have the task issuing the command exit
nvme_submit_sync_cmd() while the irq is running sync_completion().
If that happens, we could be corrupting memory, since the stack
that held 'cmdinfo' is no longer valid.

Fix this by always calling nvme_abort_cmd_info(). Once that call
completes, we know that we have either run sync_completion() if
the completion came in, or that we will never run it since we now
have special_completion() as the command callback handler.

Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
index e92bdf4c68fc..b1d5d8797315 100644
--- a/drivers/block/nvme-core.c
+++ b/drivers/block/nvme-core.c
@@ -804,12 +804,19 @@ static int nvme_submit_sync_cmd(struct request *req, struct nvme_command *cmd,
                 nvme_finish_cmd(nvmeq, req->tag, NULL);
                 set_current_state(TASK_RUNNING);
         }
-        schedule_timeout(timeout);
+        ret = schedule_timeout(timeout);
 
-        if (cmdinfo.status == -EINTR) {
-                nvme_abort_cmd_info(nvmeq, blk_mq_rq_to_pdu(req));
+        /*
+         * Ensure that sync_completion has either run, or that it will
+         * never run.
+         */
+        nvme_abort_cmd_info(nvmeq, blk_mq_rq_to_pdu(req));
+
+        /*
+         * We never got the completion
+         */
+        if (cmdinfo.status == -EINTR)
                 return -EINTR;
-        }
 
         if (result)
                 *result = cmdinfo.result;