linux-kernel - [PATCH] staging: vchiq: Fix refcounting bug in buffer_from

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Date:   Wed, 22 Jul 2020 16:06:51 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Dave Stevenson <dave.stevenson@...pberrypi.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Jamal Shareef <jamal.k.shareef@...il.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Stefan Wahren <wahrenst@....net>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] staging: vchiq: Fix refcounting bug in buffer_from_host()

If we fail to queue the buffer then it can never be dequeued.  This can
lead to a forever loop in stop_streaming() when we wait for everything
to finish.

Fixes: 70ec64ccdaac ("staging: bcm2835-camera: Ensure all buffers are returned on disable")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
>From static analysis.  Not tested.  Please review carefully etc.

 drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c b/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c
index dc767730db43..65dd2a55b3da 100644
--- a/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c
+++ b/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c
@@ -441,6 +441,8 @@ buffer_from_host(struct vchiq_mmal_instance *instance,
 	ret = vchiq_queue_kernel_message(instance->service_handle, &m,
 					 sizeof(struct mmal_msg_header) +
 					 sizeof(m.u.buffer_from_host));
+	if (ret)
+		atomic_dec(&port->buffers_with_vpu);
 
 	vchiq_release_service(instance->service_handle);
 
-- 
2.27.0