[PATCH AUTOSEL 4.19 138/146] scsi: lpfc: Correct race with abort on completion path

From: Sasha Levin
Date: Wed Oct 31 2018 - 19:07:53 EST

From: James Smart <jsmart2021@xxxxxxxxx>

[ Upstream commit ca7fb76e091f889cfda1287c07a9358f73832b39 ]

On io completion, the driver is taking an adapter wide lock and nulling the
scsi command back pointer. The nulling of the back pointer is to signify the
io was completed and the scsi_done() routine was called. However, the routine
makes no check to see if the abort routine had done the same thing and
possibly nulled the pointer. Thus it may doubly-complete the io.

Make the following mods:

- Check to make sure forward progress (call scsi_done()) only happens if the
command pointer was non-null.

- As the taking of the lock, which is adapter wide, is very costly on a system
under load, null the pointer using an xchg operation rather than under lock.

Signed-off-by: Dick Kennedy <dick.kennedy@xxxxxxxxxxxx>
Signed-off-by: James Smart <james.smart@xxxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/scsi/lpfc/lpfc_scsi.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_scsi.c b/drivers/scsi/lpfc/lpfc_scsi.c
index 5c7858e735c9..200b5bca1f5f 100644
--- a/drivers/scsi/lpfc/lpfc_scsi.c
+++ b/drivers/scsi/lpfc/lpfc_scsi.c
@@ -4158,9 +4158,17 @@ lpfc_scsi_cmd_iocb_cmpl(struct lpfc_hba *phba, struct lpfc_iocbq *pIocbIn,
lpfc_scsi_unprep_dma_buf(phba, lpfc_cmd);

- spin_lock_irqsave(&phba->hbalock, flags);
- lpfc_cmd->pCmd = NULL;
- spin_unlock_irqrestore(&phba->hbalock, flags);
+ /* If pCmd was set to NULL from abort path, do not call scsi_done */
+ if (xchg(&lpfc_cmd->pCmd, NULL) == NULL) {
+ lpfc_printf_vlog(vport, KERN_INFO, LOG_FCP,
+ "0711 FCP cmd already NULL, sid: 0x%06x, "
+ "did: 0x%06x, oxid: 0x%04x\n",
+ vport->fc_myDID,
+ (pnode) ? pnode->nlp_DID : 0,
+ phba->sli_rev == LPFC_SLI_REV4 ?
+ lpfc_cmd->cur_iocbq.sli4_xritag : 0xffff);
+ return;
+ }

/* The sdev is not guaranteed to be valid post scsi_done upcall. */