linux-kernel - [PATCH] scsi: libfc: Fix use after free in fc_exch_abts

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Date:   Thu,  3 Mar 2022 09:51:15 +0800
From:   Jianglei Nie <niejianglei2021@....com>
To:     hare@...e.de, jejb@...ux.ibm.com, martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jianglei Nie <niejianglei2021@....com>
Subject: [PATCH] scsi: libfc: Fix use after free in fc_exch_abts_resp()

fc_exch_release(ep) will decrease the ep's reference count. When the
reference count reaches zero, it is freed. But ep is still used in the
following code, which will lead to a use after free.

We should return the function after the call of fc_exch_release() to
avoid use after free.

Signed-off-by: Jianglei Nie <niejianglei2021@....com>
---
 drivers/scsi/libfc/fc_exch.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index 841000445b9a..aa223db4cf53 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -1701,6 +1701,7 @@ static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp)
 	if (cancel_delayed_work_sync(&ep->timeout_work)) {
 		FC_EXCH_DBG(ep, "Exchange timer canceled due to ABTS response\n");
 		fc_exch_release(ep);	/* release from pending timer hold */
+		return;
 	}
 
 	spin_lock_bh(&ep->ex_lock);
-- 
2.25.1