linux-kernel - [PATCH 5.15 701/917] i2c: i801: Use PCI bus rescan mutex to protect P2SB access

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Date:   Mon, 15 Nov 2021 18:03:16 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jean Delvare <jdelvare@...e.de>, Wolfram Sang <wsa@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 701/917] i2c: i801: Use PCI bus rescan mutex to protect P2SB access

From: Heiner Kallweit <hkallweit1@...il.com>

[ Upstream commit 7d6b61c394a42b8385858bb9e306d48a0112823c ]

As pointed out by Andy in [0] using a local mutex here isn't strictly
wrong but not sufficient. We should hold the PCI rescan lock for P2SB
operations.

[0] https://www.spinics.net/lists/linux-i2c/msg52717.html

Fixes: 1a987c69ce2c ("i2c: i801: make p2sb_spinlock a mutex")
Reported-by: Andy Shevchenko <andriy.shevchenko@...el.com>
Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>
Reviewed-by: Jean Delvare <jdelvare@...e.de>
Signed-off-by: Wolfram Sang <wsa@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/i2c/busses/i2c-i801.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 89ae78ef1a1cc..1f929e6c30bea 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -1493,7 +1493,6 @@ static struct platform_device *
 i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
 		 struct resource *tco_res)
 {
-	static DEFINE_MUTEX(p2sb_mutex);
 	struct resource *res;
 	unsigned int devfn;
 	u64 base64_addr;
@@ -1506,7 +1505,7 @@ i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
 	 * enumerated by the PCI subsystem, so we need to unhide/hide it
 	 * to lookup the P2SB BAR.
 	 */
-	mutex_lock(&p2sb_mutex);
+	pci_lock_rescan_remove();
 
 	devfn = PCI_DEVFN(PCI_SLOT(pci_dev->devfn), 1);
 
@@ -1524,7 +1523,7 @@ i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
 	/* Hide the P2SB device, if it was hidden before */
 	if (hidden)
 		pci_bus_write_config_byte(pci_dev->bus, devfn, 0xe1, hidden);
-	mutex_unlock(&p2sb_mutex);
+	pci_unlock_rescan_remove();
 
 	res = &tco_res[1];
 	if (pci_dev->device == PCI_DEVICE_ID_INTEL_DNV_SMBUS)
-- 
2.33.0