[PATCH 6.0 0563/1073] scsi: core: Fix a race between scsi_done() and scsi_timeout()

Greg Kroah-Hartman
2022-12-28T16:07:28Z

From: Bart Van Assche <bvanassche@acm.org>

[ 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>
---
drivers/scsi/scsi_error.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 448748e3fba5..f00212777f82 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -342,19 +342,11 @@ enum blk_eh_timer_return scsi_timeout(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);
--
2.35.1