linux-kernel - [PATCH 4.9 021/108] i2c: piix4: Request the SMBUS semaphore inside the mutex

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Date:   Thu, 15 Jun 2017 19:52:27 +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, Jean Delvare <jdelvare@...e.de>,
        Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 021/108] i2c: piix4: Request the SMBUS semaphore inside the mutex

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ricardo Ribalda <ricardo.ribalda@...il.com>


[ Upstream commit bbb27fc33d44e7b8d96369810654df4ee1837566 ]

SMBSLVCNT must be protected with the piix4_mutex_sb800 in order to avoid
multiple buses accessing to the semaphore at the same time.

Fixes: 701dc207bf55 ("i2c: piix4: Avoid race conditions with IMC")
Reported-by: Jean Delvare <jdelvare@...e.de>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Signed-off-by: Jean Delvare <jdelvare@...e.de>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/i2c/busses/i2c-piix4.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -592,6 +592,8 @@ static s32 piix4_access_sb800(struct i2c
 	u8 port;
 	int retval;
 
+	mutex_lock(&piix4_mutex_sb800);
+
 	/* Request the SMBUS semaphore, avoid conflicts with the IMC */
 	smbslvcnt  = inb_p(SMBSLVCNT);
 	do {
@@ -605,10 +607,10 @@ static s32 piix4_access_sb800(struct i2c
 		usleep_range(1000, 2000);
 	} while (--retries);
 	/* SMBus is still owned by the IMC, we give up */
-	if (!retries)
+	if (!retries) {
+		mutex_unlock(&piix4_mutex_sb800);
 		return -EBUSY;
-
-	mutex_lock(&piix4_mutex_sb800);
+	}
 
 	outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
 	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
@@ -623,11 +625,11 @@ static s32 piix4_access_sb800(struct i2c
 
 	outb_p(smba_en_lo, SB800_PIIX4_SMB_IDX + 1);
 
-	mutex_unlock(&piix4_mutex_sb800);
-
 	/* Release the semaphore */
 	outb_p(smbslvcnt | 0x20, SMBSLVCNT);
 
+	mutex_unlock(&piix4_mutex_sb800);
+
 	return retval;
 }