[PATCH 5.4.y] scsi: lpfc: Fix buffer free/clear order in deferred receive path

[Sasha Levin <sashal@kernel.org>]

From: John Evans <evans1210144@gmail.com>

[ Upstream commit 9dba9a45c348e8460da97c450cddf70b2056deb3 ]

Fix a use-after-free window by correcting the buffer release sequence in
the deferred receive path. The code freed the RQ buffer first and only
then cleared the context pointer under the lock. Concurrent paths (e.g.,
ABTS and the repost path) also inspect and release the same pointer under
the lock, so the old order could lead to double-free/UAF.

Note that the repost path already uses the correct pattern: detach the
pointer under the lock, then free it after dropping the lock. The
deferred path should do the same.

Fixes: 472e146d1cf3 ("scsi: lpfc: Correct upcalling nvmet_fc transport during io done downcall")
Cc: stable@vger.kernel.org
Signed-off-by: John Evans <evans1210144@gmail.com>
Link: https://lore.kernel.org/r/20250828044008.743-1-evans1210144@gmail.com
Reviewed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[ Adjust context ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/lpfc/lpfc_nvmet.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_nvmet.c b/drivers/scsi/lpfc/lpfc_nvmet.c
index 979a6d11b1b71..728ec3f47e023 100644
--- a/drivers/scsi/lpfc/lpfc_nvmet.c
+++ b/drivers/scsi/lpfc/lpfc_nvmet.c
@@ -1172,7 +1172,7 @@ lpfc_nvmet_defer_rcv(struct nvmet_fc_target_port *tgtport,
 	struct lpfc_nvmet_tgtport *tgtp;
 	struct lpfc_nvmet_rcv_ctx *ctxp =
 		container_of(rsp, struct lpfc_nvmet_rcv_ctx, ctx.fcp_req);
-	struct rqb_dmabuf *nvmebuf = ctxp->rqb_buffer;
+	struct rqb_dmabuf *nvmebuf;
 	struct lpfc_hba *phba = ctxp->phba;
 	unsigned long iflag;
 
@@ -1180,13 +1180,18 @@ lpfc_nvmet_defer_rcv(struct nvmet_fc_target_port *tgtport,
 	lpfc_nvmeio_data(phba, "NVMET DEFERRCV: xri x%x sz %d CPU %02x\n",
 			 ctxp->oxid, ctxp->size, raw_smp_processor_id());
 
+	spin_lock_irqsave(&ctxp->ctxlock, iflag);
+	nvmebuf = ctxp->rqb_buffer;
 	if (!nvmebuf) {
+		spin_unlock_irqrestore(&ctxp->ctxlock, iflag);
 		lpfc_printf_log(phba, KERN_INFO, LOG_NVME_IOERR,
 				"6425 Defer rcv: no buffer oxid x%x: "
 				"flg %x ste %x\n",
 				ctxp->oxid, ctxp->flag, ctxp->state);
 		return;
 	}
+	ctxp->rqb_buffer = NULL;
+	spin_unlock_irqrestore(&ctxp->ctxlock, iflag);
 
 	tgtp = phba->targetport->private;
 	if (tgtp)
@@ -1194,9 +1199,6 @@ lpfc_nvmet_defer_rcv(struct nvmet_fc_target_port *tgtport,
 
 	/* Free the nvmebuf since a new buffer already replaced it */
 	nvmebuf->hrq->rqbp->rqb_free_buffer(phba, nvmebuf);
-	spin_lock_irqsave(&ctxp->ctxlock, iflag);
-	ctxp->rqb_buffer = NULL;
-	spin_unlock_irqrestore(&ctxp->ctxlock, iflag);
 }
 
 static void
-- 
2.51.0