netdev - [PATCH AUTOSEL 4.19 12/14] sfc: extend the locking on mcdi->seqno

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Message-Id: <20220309162508.137035-12-sashal@kernel.org>
Date:   Wed,  9 Mar 2022 11:25:05 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Niels Dossche <dossche.niels@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, ecree.xilinx@...il.com,
        kuba@...nel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 12/14] sfc: extend the locking on mcdi->seqno

From: Niels Dossche <dossche.niels@...il.com>

[ Upstream commit f1fb205efb0ccca55626fd4ef38570dd16b44719 ]

seqno could be read as a stale value outside of the lock. The lock is
already acquired to protect the modification of seqno against a possible
race condition. Place the reading of this value also inside this locking
to protect it against a possible race condition.

Signed-off-by: Niels Dossche <dossche.niels@...il.com>
Acked-by: Martin Habets <habetsm.xilinx@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/sfc/mcdi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c
index dfad93fca0a6..0fa64b8b79bf 100644
--- a/drivers/net/ethernet/sfc/mcdi.c
+++ b/drivers/net/ethernet/sfc/mcdi.c
@@ -166,9 +166,9 @@ static void efx_mcdi_send_request(struct efx_nic *efx, unsigned cmd,
 	/* Serialise with efx_mcdi_ev_cpl() and efx_mcdi_ev_death() */
 	spin_lock_bh(&mcdi->iface_lock);
 	++mcdi->seqno;
+	seqno = mcdi->seqno & SEQ_MASK;
 	spin_unlock_bh(&mcdi->iface_lock);
 
-	seqno = mcdi->seqno & SEQ_MASK;
 	xflags = 0;
 	if (mcdi->mode == MCDI_MODE_EVENTS)
 		xflags |= MCDI_HEADER_XFLAGS_EVREQ;
-- 
2.34.1