staging: media: tegra-video: fix device_node use after free

commit c4d344163c3a7f90712525f931a6c016bbb35e18 upstream.

At probe time this code path is followed:

 * tegra_csi_init
   * tegra_csi_channels_alloc
     * for_each_child_of_node(node, channel) -- iterates over channels
       * automatically gets 'channel'
         * tegra_csi_channel_alloc()
           * saves into chan->of_node a pointer to the channel OF node
       * automatically gets and puts 'channel'
       * now the node saved in chan->of_node has refcount 0, can disappear
   * tegra_csi_channels_init
     * iterates over channels
       * tegra_csi_channel_init -- uses chan->of_node

After that, chan->of_node keeps storing the node until the device is
removed.

of_node_get() the node and of_node_put() it during teardown to avoid any
risk.

Fixes: 1ebaeb09830f ("media: tegra-video: Add support for external sensor capture")
Cc: stable@vger.kernel.org
Cc: Sowjanya Komatineni <skomatineni@nvidia.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/media/tegra-video/csi.c b/drivers/staging/media/tegra-video/csi.c
index 6b59ef55c525f00779b0cbd7fa573380b22cbc96..426e653bd55d55b80ef996557b641212ae262896 100644 (file)
--- a/drivers/staging/media/tegra-video/csi.c
+++ b/drivers/staging/media/tegra-video/csi.c
@@ -433,7 +433,7 @@ static int tegra_csi_channel_alloc(struct tegra_csi *csi,
        for (i = 0; i < chan->numgangports; i++)
                chan->csi_port_nums[i] = port_num + i * CSI_PORTS_PER_BRICK;
 
-       chan->of_node = node;
+       chan->of_node = of_node_get(node);
        chan->numpads = num_pads;
        if (num_pads & 0x2) {
                chan->pads[0].flags = MEDIA_PAD_FL_SINK;
@@ -641,6 +641,7 @@ static void tegra_csi_channels_cleanup(struct tegra_csi *csi)
                        media_entity_cleanup(&subdev->entity);
                }
 
+               of_node_put(chan->of_node);
                list_del(&chan->list);
                kfree(chan);
        }