linux-kernel - [PATCH 4.9 177/218] scsi: libfc: Fix use after free in fc_exch_abts

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Message-Id: <20220418121205.815454939@linuxfoundation.org>
Date:   Mon, 18 Apr 2022 14:14:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hannes Reinecke <hare@...e.de>,
        Jianglei Nie <niejianglei2021@....com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 177/218] scsi: libfc: Fix use after free in fc_exch_abts_resp()

From: Jianglei Nie <niejianglei2021@....com>

[ Upstream commit 271add11994ba1a334859069367e04d2be2ebdd4 ]

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.

Return after the fc_exch_release() call to avoid use after free.

Link: https://lore.kernel.org/r/20220303015115.459778-1-niejianglei2021@163.com
Reviewed-by: Hannes Reinecke <hare@...e.de>
Signed-off-by: Jianglei Nie <niejianglei2021@....com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 59fd6101f188..177e494b5e47 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -1663,6 +1663,7 @@ 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);
-- 
2.35.1