Re: [Patch] media: ti-vpe: cal: fix a kernel oops when unloading module

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On 04/03/2020 10:40, Tomi Valkeinen wrote:
On 03/03/2020 19:26, Benoit Parrot wrote:
After the switch to use v4l2_async_notifier_add_subdev() and
v4l2_async_notifier_cleanup(), unloading the ti_cal module would casue a
kernel oops.

This was root cause to the fact that v4l2_async_notifier_cleanup() tries
to kfree the asd pointer passed into v4l2_async_notifier_add_subdev().

In our case the asd reference was from a statically allocated struct.
So in effect v4l2_async_notifier_cleanup() was trying to free a pointer
that was not kalloc.

So here we switch to using a kzalloc struct instead of a static one.

Fixes: d079f94c9046 ("media: platform: Switch to v4l2_async_notifier_add_subdev")

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Benoit Parrot <bparrot@xxxxxx>
---
  drivers/media/platform/ti-vpe/cal.c | 7 ++++---
  1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/ti-vpe/cal.c b/drivers/media/platform/ti-vpe/cal.c
index 6d4cbb8782ed..18fe2cb9dd17 100644
--- a/drivers/media/platform/ti-vpe/cal.c
+++ b/drivers/media/platform/ti-vpe/cal.c
@@ -372,8 +372,6 @@ struct cal_ctx {
      struct v4l2_subdev    *sensor;
      struct v4l2_fwnode_endpoint    endpoint;
-    struct v4l2_async_subdev asd;
-
      struct v4l2_fh        fh;
      struct cal_dev        *dev;
      struct cc_data        *cc;
@@ -2032,7 +2030,6 @@ static int of_cal_create_instance(struct cal_ctx *ctx, int inst)
      parent = pdev->dev.of_node;
-    asd = &ctx->asd;
      endpoint = &ctx->endpoint;
      ep_node = NULL;
@@ -2040,6 +2037,10 @@ static int of_cal_create_instance(struct cal_ctx *ctx, int inst)
      sensor_node = NULL;
      ret = -EINVAL;
+    asd = kzalloc(sizeof(*asd), GFP_KERNEL);
+    if (!asd)
+        goto cleanup_exit;
+
      ctx_dbg(3, ctx, "Scanning Port node for csi2 port: %d\n", inst);
      for (index = 0; index < CAL_NUM_CSI2_PORTS; index++) {
          port = of_get_next_port(parent, port);


Thanks, this fixes the crash for me.

It does look a bit odd that something is allocated with kzalloc, and then it's freed somewhere inside v4l2_async_notifier_cleanup, though. But if that's how it supposed to be used, looks fine to me.

Well, sent that a few seconds too early... With this patch, I see kmemleaks.

 Tomi

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