[PATCH] drm/tegra: dc: fix reference leak in tegra_dc_couple()

[PATCH] drm/tegra: dc: fix reference leak in tegra_dc_couple()

[Ma Ke]

driver_find_device() calls get_device() to increment the reference
count once a matching device is found, but there is no put_device() to
balance the reference count. To avoid reference count leakage, add
put_device() to decrease the reference count.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: a31500fe7055 ("drm/tegra: dc: Restore coupling of display controllers")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 drivers/gpu/drm/tegra/dc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 59d5c1ba145a..6c84bd69b11f 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -3148,6 +3148,7 @@ static int tegra_dc_couple(struct tegra_dc *dc)
 		dc->client.parent = &parent->client;
 
 		dev_dbg(dc->dev, "coupled to %s\n", dev_name(companion));
+		put_device(companion);
 	}
 
 	return 0;
-- 
2.17.1

Re: [PATCH] drm/tegra: dc: fix reference leak in tegra_dc_couple()

[Markus Elfring]

> driver_find_device() calls get_device() to increment the reference
> count once a matching device is found, but there is no put_device() to
> balance the reference count. To avoid reference count leakage, add
> put_device() to decrease the reference count.

How do you think about to increase the application of scope-based resource management?
https://elixir.bootlin.com/linux/v6.17-rc7/source/include/linux/device.h#L1180

Regards,
Markus

Re: [PATCH] drm/tegra: dc: fix reference leak in tegra_dc_couple()

[Greg KH]

On Sat, Sep 27, 2025 at 02:43:17PM +0200, Markus Elfring wrote:
> > driver_find_device() calls get_device() to increment the reference
> > count once a matching device is found, but there is no put_device() to
> > balance the reference count. To avoid reference count leakage, add
> > put_device() to decrease the reference count.
> 
> How do you think about to increase the application of scope-based resource management?
> https://elixir.bootlin.com/linux/v6.17-rc7/source/include/linux/device.h#L1180


Hi,

This is the semi-friendly patch-bot of Greg Kroah-Hartman.

Markus, you seem to have sent a nonsensical or otherwise pointless
review comment to a patch submission on a Linux kernel developer mailing
list.  I strongly suggest that you not do this anymore.  Please do not
bother developers who are actively working to produce patches and
features with comments that, in the end, are a waste of time.

Patch submitter, please ignore Markus's suggestion; you do not need to
follow it at all.  The person/bot/AI that sent it is being ignored by
almost all Linux kernel maintainers for having a persistent pattern of
behavior of producing distracting and pointless commentary, and
inability to adapt to feedback.  Please feel free to also ignore emails
from them.

thanks,

greg k-h's patch email bot