[PATCH 6/8] block: drivers: complete request locally from blk_mq_tagset_busy_iter

[Ming Lei]

It can be a bit hard for driver to avoid request UAF between normal
completion and completion via blk_mq_tagset_busy_iter() if async
completion is done in blk_mq_tagset_busy_iter(). Cause request->tag
is only freed after .mq_ops->complete() is called, and rquest->tag
may still be valid after blk_mq_complete_request() is returned from
normal completion path, so this request is still visible in
blk_mq_tagset_busy_iter().

This patch itself can't avoid such request UAF completely. We will
grab a request reference in next patch when walking request via
blk_mq_tagset_busy_iter() for fixing such race, that is why we have
to convert to blk_mq_complete_request_locally() first.

Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 drivers/block/mtip32xx/mtip32xx.c | 2 +-
 drivers/block/nbd.c               | 2 +-
 drivers/nvme/host/core.c          | 2 +-
 drivers/scsi/scsi_lib.c           | 6 +++++-
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 3be0dbc674bd..05f5e36ee608 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -3748,7 +3748,7 @@ static bool mtip_no_dev_cleanup(struct request *rq, void *data, bool reserv)
 	struct mtip_cmd *cmd = blk_mq_rq_to_pdu(rq);
 
 	cmd->status = BLK_STS_IOERR;
-	blk_mq_complete_request(rq);
+	blk_mq_complete_request_locally(rq);
 	return true;
 }
 
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 4ff71b579cfc..3dcf3288efa8 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -809,7 +809,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved)
 	cmd->status = BLK_STS_IOERR;
 	mutex_unlock(&cmd->lock);
 
-	blk_mq_complete_request(req);
+	blk_mq_complete_request_locally(req);
 	return true;
 }
 
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 0896e21642be..a605954477da 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -381,7 +381,7 @@ bool nvme_cancel_request(struct request *req, void *data, bool reserved)
 
 	nvme_req(req)->status = NVME_SC_HOST_ABORTED_CMD;
 	nvme_req(req)->flags |= NVME_REQ_CANCELLED;
-	blk_mq_complete_request(req);
+	blk_mq_complete_request_locally(req);
 	return true;
 }
 EXPORT_SYMBOL_GPL(nvme_cancel_request);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index c289991ffaed..7cbaee282b6d 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1568,7 +1568,11 @@ static void scsi_mq_done(struct scsi_cmnd *cmd)
 	if (unlikely(test_and_set_bit(SCMD_STATE_COMPLETE, &cmd->state)))
 		return;
 	trace_scsi_dispatch_cmd_done(cmd);
-	blk_mq_complete_request(cmd->request);
+
+	if (unlikely(host_byte(cmd->result) != DID_OK))
+		blk_mq_complete_request_locally(cmd->request);
+	else
+		blk_mq_complete_request(cmd->request);
 }
 
 static void scsi_mq_put_budget(struct request_queue *q)
-- 
2.29.2