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[PATCH] [media] Siano: Use common error handling code in smsusb_init_device()

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  [PATCH] [media] Siano: Use common error handling code in  smsusb_init_device() SF Markus Elfring <elfring@users.sourceforge.net> - 2017-09-20 14:50 +0200
    Re: [PATCH] [media] Siano: Use common error handling code in  smsusb_init_device() Dan Carpenter <dan.carpenter@oracle.com> - 2017-09-20 16:00 +0200
      Re: [media] Siano: Use common error handling code in  smsusb_init_device() SF Markus Elfring <elfring@users.sourceforge.net> - 2017-09-20 19:20 +0200

#1735754 — [PATCH] [media] Siano: Use common error handling code in smsusb_init_device()

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Wed, 20 Sep 2017 14:30:55 +0200

Add a jump target so that a bit of exception handling can be better
reused at the end of this function.

This refactoring might fix also an error situation where the
function "kfree" was not called after a software failure
was noticed in two cases.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 drivers/media/usb/siano/smsusb.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/media/usb/siano/smsusb.c b/drivers/media/usb/siano/smsusb.c
index 8c1f926567ec..b8e7b05cf6d0 100644
--- a/drivers/media/usb/siano/smsusb.c
+++ b/drivers/media/usb/siano/smsusb.c
@@ -458,12 +458,10 @@ static int smsusb_init_device(struct usb_interface *intf, int board_id)
 	rc = smscore_register_device(&params, &dev->coredev, mdev);
 	if (rc < 0) {
 		pr_err("smscore_register_device(...) failed, rc %d\n", rc);
-		smsusb_term_device(intf);
 #ifdef CONFIG_MEDIA_CONTROLLER_DVB
 		media_device_unregister(mdev);
 #endif
-		kfree(mdev);
-		return rc;
+		goto terminate_device;
 	}
 
 	smscore_set_board_id(dev->coredev, board_id);
@@ -480,8 +478,7 @@ static int smsusb_init_device(struct usb_interface *intf, int board_id)
 	rc = smsusb_start_streaming(dev);
 	if (rc < 0) {
 		pr_err("smsusb_start_streaming(...) failed\n");
-		smsusb_term_device(intf);
-		return rc;
+		goto terminate_device;
 	}
 
 	dev->state = SMSUSB_ACTIVE;
@@ -489,13 +486,17 @@ static int smsusb_init_device(struct usb_interface *intf, int board_id)
 	rc = smscore_start_device(dev->coredev);
 	if (rc < 0) {
 		pr_err("smscore_start_device(...) failed\n");
-		smsusb_term_device(intf);
-		return rc;
+		goto terminate_device;
 	}
 
 	pr_debug("device 0x%p created\n", dev);
 
 	return rc;
+
+terminate_device:
+	smsusb_term_device(intf);
+	kfree(mdev);
+	return rc;
 }
 
 static int smsusb_probe(struct usb_interface *intf,
-- 
2.14.1

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#1735783

On Wed, Sep 20, 2017 at 02:40:28PM +0200, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Wed, 20 Sep 2017 14:30:55 +0200
> 
> Add a jump target so that a bit of exception handling can be better
> reused at the end of this function.
> 
> This refactoring might fix also an error situation where the
> function "kfree" was not called after a software failure
> was noticed in two cases.
> 

No.  It doesn't fix a leak, it introduces a double free.  If
smscore_register_device() succeeds then mdev is freed when we call
smsusb_term_device(intf);  The call tree is:

smsusb_term_device()
 -> smscore_unregister_device()
    -> smscore_notify_clients()
       -> smsdvb_onremove()
          -> smsdvb_unregister_client()
             -> smsdvb_media_device_unregister()
                -> kfree(coredev->media_dev);

regards,
dan carpenter

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#1735935 — Re: [media] Siano: Use common error handling code in smsusb_init_device()

> If smscore_register_device() succeeds then mdev is freed when we call
> smsusb_term_device(intf);  The call tree is:

Thanks for your constructive information.


How do you think about another implementation detail in this function then?

May the statement “kfree(mdev);” be executed before “smsusb_term_device(intf);”
in one if branch?

Regards,
Markus

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