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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Saubhik Mukherjee <saubhik.mukherjee@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.4 12/34] net: appletalk: cops: Fix data race in cops_probe1
Date:   Mon, 14 Jun 2021 12:27:03 +0200
Message-Id: <20210614102641.986810199@linuxfoundation.org>
In-Reply-To: <20210614102641.582612289@linuxfoundation.org>
References: <20210614102641.582612289@linuxfoundation.org>
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From: Saubhik Mukherjee <saubhik.mukherjee@gmail.com>

[ Upstream commit a4dd4fc6105e54393d637450a11d4cddb5fabc4f ]

In cops_probe1(), there is a write to dev->base_addr after requesting an
interrupt line and registering the interrupt handler cops_interrupt().
The handler might be called in parallel to handle an interrupt.
cops_interrupt() tries to read dev->base_addr leading to a potential
data race. So write to dev->base_addr before calling request_irq().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Saubhik Mukherjee <saubhik.mukherjee@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/appletalk/cops.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/appletalk/cops.c b/drivers/net/appletalk/cops.c
index 7f2a032c354c..841a5de58c7c 100644
--- a/drivers/net/appletalk/cops.c
+++ b/drivers/net/appletalk/cops.c
@@ -324,6 +324,8 @@ static int __init cops_probe1(struct net_device *dev, int ioaddr)
 			break;
 	}
 
+	dev->base_addr = ioaddr;
+
 	/* Reserve any actual interrupt. */
 	if (dev->irq) {
 		retval = request_irq(dev->irq, cops_interrupt, 0, dev->name, dev);
@@ -331,8 +333,6 @@ static int __init cops_probe1(struct net_device *dev, int ioaddr)
 			goto err_out;
 	}
 
-	dev->base_addr = ioaddr;
-
         lp = netdev_priv(dev);
         spin_lock_init(&lp->lock);
 
-- 
2.30.2