[PATCH] comedi: comedi_bond: Fix leak of opened device references

[Ian Abbott <abbotti@mev.co.uk>]

bonding_attach() calls do_dev_config() to open other comedi devices
specified by the user and tries to make use of them as part of the
'bonding' device.  If it successfully opens the other device but cannot
use it (either because it does not any subdevices of a type the
'bonding' device can use, or because of some error that occurs while
dealing with its subdevices) then it is left in the open state and the
fact that it is open does not get recorded by the 'bonding' device, so
the reference to the opened device gets lost.  Fix it by closing the
opened device if it could not be bound to the 'bonding' device.

To match previous behavior, if the opened device is unsuitable then
ignore it (after closing it).  The opened devices recorded by the
'bonding' device will eventually get closed by bonding_detach() even if
bonding_attach() returns an error.

Fixes: 3cf840f65ad5 ("Staging: comedi: add comedi_bond driver")
Reported-by: Wentao Liang <vulab@iscas.ac.cn>
Link: https://lore.kernel.org/lkml/20261103063301.1025860-1-vulab@iscas.ac.cn
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
---
 drivers/comedi/drivers/comedi_bond.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/comedi/drivers/comedi_bond.c b/drivers/comedi/drivers/comedi_bond.c
index a10cfbd04c728..3764ece90f826 100644
--- a/drivers/comedi/drivers/comedi_bond.c
+++ b/drivers/comedi/drivers/comedi_bond.c
@@ -184,7 +184,9 @@ static int do_dev_config(struct comedi_device *dev, struct comedi_devconfig *it)
 		char file[sizeof("/dev/comediXXXXXX")];
 		int minor = it->options[i];
 		struct comedi_device *d;
-		int sdev = -1, nchans;
+		int sdev = -1;
+		int nchans;
+		int nope = 1;
 		struct bonded_device *bdev;
 		struct bonded_device **devs;
 
@@ -223,11 +225,14 @@ static int do_dev_config(struct comedi_device *dev, struct comedi_devconfig *it)
 				dev_err(dev->class_dev,
 					"comedi_get_n_channels() returned %d on minor %u subdev %d!\n",
 					nchans, minor, sdev);
-				return -EINVAL;
+				nope = -EINVAL;
+				break;
 			}
 			bdev = kmalloc_obj(*bdev);
-			if (!bdev)
-				return -ENOMEM;
+			if (!bdev) {
+				nope = -ENOMEM;
+				break;
+			}
 
 			bdev->dev = d;
 			bdev->minor = minor;
@@ -248,14 +253,23 @@ static int do_dev_config(struct comedi_device *dev, struct comedi_devconfig *it)
 				dev_err(dev->class_dev,
 					"Could not allocate memory. Out of memory?\n");
 				kfree(bdev);
-				return -ENOMEM;
+				nope = -ENOMEM;
+				break;
 			}
 			devpriv->devs = devs;
 			devpriv->devs[devpriv->ndevs++] = bdev;
+			nope = 0;	/* keeps the device open */
 
 			/* Append dev:subdev to devpriv->name */
 			seq_buf_printf(&s, "%u:%u ", bdev->minor, bdev->subdev);
 		}
+
+		if (nope) {
+			/* Opened device cannot be used, so close it. */
+			comedi_close_from(d, dev->minor);
+			if (nope < 0)
+				return nope;
+		}
 	}
 
 	if (!devpriv->nchans) {
-- 
2.53.0