scsi: core: Fix a race between scsi_done() and scsi_timeout()

[ Upstream commit 978b7922d3dca672b41bb4b8ce6c06ab77112741 ]

If there is a race between scsi_done() and scsi_timeout() and if
scsi_timeout() loses the race, scsi_timeout() should not reset the request
timer. Hence change the return value for this case from BLK_EH_RESET_TIMER
into BLK_EH_DONE.

Although the block layer holds a reference on a request (req->ref) while
calling a timeout handler, restarting the timer (blk_add_timer()) while a
request is being completed is racy.

Reviewed-by: Mike Christie <michael.christie@oracle.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Hannes Reinecke <hare@suse.de>
Reported-by: Adrian Hunter <adrian.hunter@intel.com>
Fixes: 15f73f5b3e59 ("blk-mq: move failure injection out of blk_mq_complete_request")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20221018202958.1902564-2-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index bb5a6e0..dd9f577 100644 (file)
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -343,19 +343,11 @@ enum blk_eh_timer_return scsi_times_out(struct request *req)
 
        if (rtn == BLK_EH_DONE) {
                /*
-                * Set the command to complete first in order to prevent a real
-                * completion from releasing the command while error handling
-                * is using it. If the command was already completed, then the
-                * lower level driver beat the timeout handler, and it is safe
-                * to return without escalating error recovery.
-                *
-                * If timeout handling lost the race to a real completion, the
-                * block layer may ignore that due to a fake timeout injection,
-                * so return RESET_TIMER to allow error handling another shot
-                * at this command.
+                * If scsi_done() has already set SCMD_STATE_COMPLETE, do not
+                * modify *scmd.
                 */
                if (test_and_set_bit(SCMD_STATE_COMPLETE, &scmd->state))
-                       return BLK_EH_RESET_TIMER;
+                       return BLK_EH_DONE;
                if (scsi_abort_command(scmd) != SUCCESS) {
                        set_host_byte(scmd, DID_TIME_OUT);
                        scsi_eh_scmd_add(scmd);