[PATCH] staging: media: tegra-video: fix device_node use after free

luca.ceresoli
2022-10-28T08:19:50Z

From: Luca Ceresoli <luca.ceresoli@bootlin.com>

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>
---
drivers/staging/media/tegra-video/csi.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/tegra-video/csi.c b/drivers/staging/media/tegra-video/csi.c
index b26e44adb2be..1b05f620b476 100644
--- 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;
@@ -640,6 +640,7 @@ 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);
}
--
2.34.1