linux-kernel - [PATCH 5.7 082/244] dmaengine: idxd: fix cdev locking for open and release

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Message-Id: <20200720152829.742328308@linuxfoundation.org>
Date:   Mon, 20 Jul 2020 17:35:53 +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, Nikhil Rao <nikhil.rao@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.7 082/244] dmaengine: idxd: fix cdev locking for open and release

From: Nikhil Rao <nikhil.rao@...el.com>

[ Upstream commit 66983bc18fad17d10766650b3685045f6f092d73 ]

add the wq lock in cdev open and release call. This fixes
race conditions observed in the open and close routines.

Fixes: 42d279f9137a ("dmaengine: idxd: add char driver to expose submission portal to userland")
Signed-off-by: Nikhil Rao <nikhil.rao@...el.com>
Signed-off-by: Dave Jiang <dave.jiang@...el.com>
Link: https://lore.kernel.org/r/159285824892.64944.2905413694915141834.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/dma/idxd/cdev.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
index ff49847e37a86..cb376cf6a2d2c 100644
--- a/drivers/dma/idxd/cdev.c
+++ b/drivers/dma/idxd/cdev.c
@@ -74,6 +74,7 @@ static int idxd_cdev_open(struct inode *inode, struct file *filp)
 	struct idxd_device *idxd;
 	struct idxd_wq *wq;
 	struct device *dev;
+	int rc = 0;
 
 	wq = inode_wq(inode);
 	idxd = wq->idxd;
@@ -81,17 +82,27 @@ static int idxd_cdev_open(struct inode *inode, struct file *filp)
 
 	dev_dbg(dev, "%s called: %d\n", __func__, idxd_wq_refcount(wq));
 
-	if (idxd_wq_refcount(wq) > 0 && wq_dedicated(wq))
-		return -EBUSY;
-
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;
 
+	mutex_lock(&wq->wq_lock);
+
+	if (idxd_wq_refcount(wq) > 0 && wq_dedicated(wq)) {
+		rc = -EBUSY;
+		goto failed;
+	}
+
 	ctx->wq = wq;
 	filp->private_data = ctx;
 	idxd_wq_get(wq);
+	mutex_unlock(&wq->wq_lock);
 	return 0;
+
+ failed:
+	mutex_unlock(&wq->wq_lock);
+	kfree(ctx);
+	return rc;
 }
 
 static int idxd_cdev_release(struct inode *node, struct file *filep)
@@ -105,7 +116,9 @@ static int idxd_cdev_release(struct inode *node, struct file *filep)
 	filep->private_data = NULL;
 
 	kfree(ctx);
+	mutex_lock(&wq->wq_lock);
 	idxd_wq_put(wq);
+	mutex_unlock(&wq->wq_lock);
 	return 0;
 }
 
-- 
2.25.1