linux-kernel - [PATCH AUTOSEL 4.14 118/127] rapidio: avoid data race between file operation callbacks and mport_cdev

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Date:   Thu, 17 Sep 2020 22:12:11 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexandre Bounine <alex.bou9@...il.com>,
        Matt Porter <mporter@...nel.crashing.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Mike Marshall <hubcap@...ibond.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ira Weiny <ira.weiny@...el.com>,
        Allison Randal <allison@...utok.net>,
        Pavel Andrianov <andrianov@...ras.ru>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.14 118/127] rapidio: avoid data race between file operation callbacks and mport_cdev_add().

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

[ Upstream commit e1c3cdb26ab881b77486dc50370356a349077c74 ]

Fields of md(mport_dev) are set after cdev_device_add().  However, the
file operation callbacks can be called after cdev_device_add() and
therefore accesses to fields of md in the callbacks can race with the rest
of the mport_cdev_add() function.

One such example is INIT_LIST_HEAD(&md->portwrites) in mport_cdev_add(),
the list is initialised after cdev_device_add().  This can race with
list_add_tail(&pw_filter->md_node,&md->portwrites) in
rio_mport_add_pw_filter() which is called by unlocked_ioctl.

To avoid such data races use cdev_device_add() after initializing md.

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

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Acked-by: Alexandre Bounine <alex.bou9@...il.com>
Cc: Matt Porter <mporter@...nel.crashing.org>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Mike Marshall <hubcap@...ibond.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Allison Randal <allison@...utok.net>
Cc: Pavel Andrianov <andrianov@...ras.ru>
Link: http://lkml.kernel.org/r/20200426112950.1803-1-madhuparnabhowmik10@gmail.com
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/rapidio/devices/rio_mport_cdev.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
index f15f6d1e1070a..f207f8725993c 100644
--- a/drivers/rapidio/devices/rio_mport_cdev.c
+++ b/drivers/rapidio/devices/rio_mport_cdev.c
@@ -2464,13 +2464,6 @@ static struct mport_dev *mport_cdev_add(struct rio_mport *mport)
 	cdev_init(&md->cdev, &mport_fops);
 	md->cdev.owner = THIS_MODULE;
 
-	ret = cdev_device_add(&md->cdev, &md->dev);
-	if (ret) {
-		rmcd_error("Failed to register mport %d (err=%d)",
-		       mport->id, ret);
-		goto err_cdev;
-	}
-
 	INIT_LIST_HEAD(&md->doorbells);
 	spin_lock_init(&md->db_lock);
 	INIT_LIST_HEAD(&md->portwrites);
@@ -2490,6 +2483,13 @@ static struct mport_dev *mport_cdev_add(struct rio_mport *mport)
 #else
 	md->properties.transfer_mode |= RIO_TRANSFER_MODE_TRANSFER;
 #endif
+
+	ret = cdev_device_add(&md->cdev, &md->dev);
+	if (ret) {
+		rmcd_error("Failed to register mport %d (err=%d)",
+		       mport->id, ret);
+		goto err_cdev;
+	}
 	ret = rio_query_mport(mport, &attr);
 	if (!ret) {
 		md->properties.flags = attr.flags;
-- 
2.25.1