patch "staging: comedi: Fix comedi_device refcnt leak in comedi_open" added to staging-linus

This is a note to let you know that I've just added the patch titled

staging: comedi: Fix comedi_device refcnt leak in comedi_open

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 332e0e17ad49e084b7db670ef43b5eb59abd9e34 Mon Sep 17 00:00:00 2001
From: Xiyu Yang <[email protected]>
Date: Mon, 20 Apr 2020 13:44:16 +0800
Subject: staging: comedi: Fix comedi_device refcnt leak in comedi_open

comedi_open() invokes comedi_dev_get_from_minor(), which returns a reference of the COMEDI device to "dev" with increased refcount.

When comedi_open() returns, "dev" becomes invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of comedi_open(). When "cfp" allocation is failed, the refcnt increased by comedi_dev_get_from_minor() is not decreased, causing a refcnt leak.

Fix this issue by calling comedi_dev_put() on this error path when "cfp" allocation is failed.

---
 drivers/staging/comedi/comedi_fops.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

index 08d1bbbebf2d..e84b4fb493d6 100644
@@ -2725,8 +2725,10 @@ static int comedi_open(struct inode *inode, struct file *file)
 	}
 
 	cfp = kzalloc(sizeof(*cfp), GFP_KERNEL);
-	if (!cfp)
+	if (!cfp) {
+		comedi_dev_put(dev);
 		return -ENOMEM;
+	}
 
 	cfp->dev = dev;
 

2.26.2