linux-kernel - [PATCH] scsi: lpfc: Fix buffer free/clear order in deferred receive path

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Message-ID: <20250826195645.720-1-evans1210144@gmail.com>
Date: Tue, 26 Aug 2025 15:56:45 -0400
From: John Evans <evans1210144@...il.com>
To: james.smart@...adcom.com,
	dick.kennedy@...adcom.com,
	James.Bottomley@...senPartnership.com,
	martin.petersen@...cle.com
Cc: linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH] scsi: lpfc: Fix buffer free/clear order in deferred receive path

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@...r.kernel.org
Signed-off-by: John Evans <evans1210144@...il.com>
---
 drivers/scsi/lpfc/lpfc_nvmet.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_nvmet.c b/drivers/scsi/lpfc/lpfc_nvmet.c
index fba2e62027b7..766319543680 100644
--- a/drivers/scsi/lpfc/lpfc_nvmet.c
+++ b/drivers/scsi/lpfc/lpfc_nvmet.c
@@ -1264,10 +1264,15 @@ lpfc_nvmet_defer_rcv(struct nvmet_fc_target_port *tgtport,
 		atomic_inc(&tgtp->rcv_fcp_cmd_defer);
 
 	/* 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);
+	nvmebuf = ctxp->rqb_buffer;
+	if (nvmebuf) {
+		ctxp->rqb_buffer = NULL;
+		spin_unlock_irqrestore(&ctxp->ctxlock, iflag);
+		nvmebuf->hrq->rqbp->rqb_free_buffer(phba, nvmebuf);
+	} else {
+		spin_unlock_irqrestore(&ctxp->ctxlock, iflag);
+	}
 }
 
 /**
-- 
2.43.0