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

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Message-ID: <4010c13f-6a32-f3c3-5b6d-62a4e3782c64@ti.com>
Date:   Wed, 4 Mar 2020 10:40:03 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Benoit Parrot <bparrot@...com>, Hans Verkuil <hverkuil@...all.nl>
CC:     <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [Patch] media: ti-vpe: cal: fix a kernel oops when unloading
 module

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@...r.kernel.org
> Signed-off-by: Benoit Parrot <bparrot@...com>
> ---
>   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.

Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...com>

  Tomi

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