scsi: set timed out out mq requests to complete

The scsi block layer requires requests claimed by the error handling be
completed by the error handler. A previous commit allowed completions
to proceed for blk-mq, breaking that assumption.

This patch prevents completions that may race with the timeout handler
by marking the state to complete, restoring the previous behavior.

Fixes: 12f5b931 ("blk-mq: Remove generation seqeunce")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 8932ae81a15a..2715cdaa669c 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -296,6 +296,20 @@ enum blk_eh_timer_return scsi_times_out(struct request *req)
                 rtn = host->hostt->eh_timed_out(scmd);
 
         if (rtn == BLK_EH_DONE) {
+                /*
+                 * For blk-mq, we must set the request state to complete now
+                 * before sending the request to the scsi error handler. This
+                 * will prevent a use-after-free in the event the LLD manages
+                 * to complete the request before the error handler finishes
+                 * processing this timed out request.
+                 *
+                 * If the request was already completed, then the LLD beat the
+                 * time out handler from transferring the request to the scsi
+                 * error handler. In that case we can return immediately as no
+                 * further action is required.
+                 */
+                if (req->q->mq_ops && !blk_mq_mark_complete(req))
+                        return rtn;
                 if (scsi_abort_command(scmd) != SUCCESS) {
                         set_host_byte(scmd, DID_TIME_OUT);
                         scsi_eh_scmd_add(scmd);