[PATCH v2 1/2] staging: media: tegra-video: fix chan->mipi value on error

[PATCH v2 1/2] staging: media: tegra-video: fix chan->mipi value on error

[luca.ceresoli]

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

chan->mipi takes the return value of tegra_mipi_request() which can be a
valid pointer or an error. However chan->mipi is checked in several places,
including error-cleanup code in tegra_csi_channels_cleanup(), as 'if
(chan->mipi)', which suggests the initial intent was that chan->mipi should
be either NULL or a valid pointer, never an error. As a consequence,
cleanup code in case of tegra_mipi_request() errors would dereference an
invalid pointer.

Fix by ensuring chan->mipi always contains either NULL or a void pointer.

Also add that to the documentation.

Fixes: 523c857e34ce ("media: tegra-video: Add CSI MIPI pads calibration")
Cc: stable@vger.kernel.org
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

---

This patch was added in v2.
---
 drivers/staging/media/tegra-video/csi.c | 1 +
 drivers/staging/media/tegra-video/csi.h | 2 +-
 2 files 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..6b59ef55c525 100644
--- a/drivers/staging/media/tegra-video/csi.c
+++ b/drivers/staging/media/tegra-video/csi.c
@@ -448,6 +448,7 @@ static int tegra_csi_channel_alloc(struct tegra_csi *csi,
 	chan->mipi = tegra_mipi_request(csi->dev, node);
 	if (IS_ERR(chan->mipi)) {
 		ret = PTR_ERR(chan->mipi);
+		chan->mipi = NULL;
 		dev_err(csi->dev, "failed to get mipi device: %d\n", ret);
 	}
 
diff --git a/drivers/staging/media/tegra-video/csi.h b/drivers/staging/media/tegra-video/csi.h
index 4ee05a1785cf..6960ea2e3d36 100644
--- a/drivers/staging/media/tegra-video/csi.h
+++ b/drivers/staging/media/tegra-video/csi.h
@@ -56,7 +56,7 @@ struct tegra_csi;
  * @framerate: active framerate for TPG
  * @h_blank: horizontal blanking for TPG active format
  * @v_blank: vertical blanking for TPG active format
- * @mipi: mipi device for corresponding csi channel pads
+ * @mipi: mipi device for corresponding csi channel pads, or NULL if not applicable (TPG, error)
  * @pixel_rate: active pixel rate from the sensor on this channel
  */
 struct tegra_csi_channel {
-- 
2.34.1

[PATCH v2 2/2] staging: media: tegra-video: fix device_node use after free

[luca.ceresoli]

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>

---

No changes in v2.
---
 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 6b59ef55c525..426e653bd55d 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;
@@ -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);
 	}
-- 
2.34.1