[PATCH] i2c: i801: Don't generate an interrupt on bus reset

From: Jean Delvare <jdelvare@suse.de>
To: Linux I2C <linux-i2c@vger.kernel.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Jarkko Nikula <jarkko.nikula@linux.intel.com>,
	Heiner Kallweit <hkallweit1@gmail.com>
Subject: [PATCH] i2c: i801: Don't generate an interrupt on bus reset
Date: Tue, 25 May 2021 17:03:36 +0200	[thread overview]
Message-ID: <20210525170336.213a19b4@endymion> (raw)

Now that the i2c-i801 driver supports interrupts, setting the KILL bit
in a attempt to recover from a timed out transaction triggers an
interrupt. Unfortunately, the interrupt handler (i801_isr) is not
prepared for this situation and will try to process the interrupt as
if it was signaling the end of a successful transaction. In the case
of a block transaction, this can result in an out-of-range memory
access.

This condition was reproduced several times by syzbot:
https://syzkaller.appspot.com/bug?extid=ed71512d469895b5b34e
https://syzkaller.appspot.com/bug?extid=8c8dedc0ba9e03f6c79e
https://syzkaller.appspot.com/bug?extid=c8ff0b6d6c73d81b610e
https://syzkaller.appspot.com/bug?extid=33f6c360821c399d69eb
https://syzkaller.appspot.com/bug?extid=be15dc0b1933f04b043a
https://syzkaller.appspot.com/bug?extid=b4d3fd1dfd53e90afd79

So disable interrupts while trying to reset the bus. Interrupts will
be enabled again for the following transaction.

Fixes: 636752bcb517 ("i2c-i801: Enable IRQ for SMBus transactions")
Reported-by: syzbot+b4d3fd1dfd53e90afd79@syzkaller.appspotmail.com
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
---
 drivers/i2c/busses/i2c-i801.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- linux-5.12.orig/drivers/i2c/busses/i2c-i801.c	2021-05-24 12:00:59.307576983 +0200
+++ linux-5.12/drivers/i2c/busses/i2c-i801.c	2021-05-24 12:04:10.230998259 +0200
@@ -401,11 +401,9 @@ static int i801_check_post(struct i801_p
 		dev_err(&priv->pci_dev->dev, "Transaction timeout\n");
 		/* try to stop the current command */
 		dev_dbg(&priv->pci_dev->dev, "Terminating the current operation\n");
-		outb_p(inb_p(SMBHSTCNT(priv)) | SMBHSTCNT_KILL,
-		       SMBHSTCNT(priv));
+		outb_p(SMBHSTCNT_KILL, SMBHSTCNT(priv));
 		usleep_range(1000, 2000);
-		outb_p(inb_p(SMBHSTCNT(priv)) & (~SMBHSTCNT_KILL),
-		       SMBHSTCNT(priv));
+		outb_p(0, SMBHSTCNT(priv));
 
 		/* Check if it worked */
 		status = inb_p(SMBHSTSTS(priv));

-- 
Jean Delvare
SUSE L3 Support
