[PATCH V2 1/2] scsi: ufs: core: Fix task management completion timeout race

[Adrian Hunter <adrian.hunter@intel.com>]

__ufshcd_issue_tm_cmd() clears req->end_io_data after timing out,
which races with the completion function ufshcd_tmc_handler() which
expects req->end_io_data to have a value.

Note __ufshcd_issue_tm_cmd() and ufshcd_tmc_handler() are already
synchronized using hba->tmf_rqs and hba->outstanding_tasks under the
host_lock spinlock.

It is also not necessary (nor typical) to clear req->end_io_data because
the block layer does it before allocating out requests e.g. via
blk_get_request().

So fix by not clearing it.

Fixes: f5ef336fd2e4c3 ("scsi: ufs: core: Fix task management completion")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/ufs/ufshcd.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 470affdec426..a904531ba528 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6616,11 +6616,6 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba,
 	err = wait_for_completion_io_timeout(&wait,
 			msecs_to_jiffies(TM_CMD_TIMEOUT));
 	if (!err) {
-		/*
-		 * Make sure that ufshcd_compl_tm() does not trigger a
-		 * use-after-free.
-		 */
-		req->end_io_data = NULL;
 		ufshcd_add_tm_upiu_trace(hba, task_tag, UFS_TM_ERR);
 		dev_err(hba->dev, "%s: task management cmd 0x%.2x timed-out\n",
 				__func__, tm_function);
-- 
2.25.1