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

[Tomi Valkeinen]

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>
> > ---
> > Â drivers/media/platform/ti-vpe/cal.c | 7 ++++---
> > Â 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 {
> > ÂÂÂÂÂ struct v4l2_subdevÂÂÂ *sensor;
> > ÂÂÂÂÂ struct v4l2_fwnode_endpointÂÂÂ endpoint;
> > -ÂÂÂ struct v4l2_async_subdev asd;
> > -
> > ÂÂÂÂÂ struct v4l2_fhÂÂÂÂÂÂÂ fh;
> > ÂÂÂÂÂ struct cal_devÂÂÂÂÂÂÂ *dev;
> > ÂÂÂÂÂ struct cc_dataÂÂÂÂÂÂÂ *cc;
> > @@ -2032,7 +2030,6 @@ static int of_cal_create_instance(struct cal_ctx *ctx, int inst)
> > ÂÂÂÂÂ parent = pdev->dev.of_node;
> > -ÂÂÂ asd = &ctx->asd;
> > ÂÂÂÂÂ endpoint = &ctx->endpoint;
> > ÂÂÂÂÂ ep_node = NULL;
> > @@ -2040,6 +2037,10 @@ static int of_cal_create_instance(struct cal_ctx *ctx, int inst)
> > ÂÂÂÂÂ sensor_node = NULL;
> > ÂÂÂÂÂ ret = -EINVAL;
> > +ÂÂÂ asd = kzalloc(sizeof(*asd), GFP_KERNEL);
> > +ÂÂÂ if (!asd)
> > +ÂÂÂÂÂÂÂ goto cleanup_exit;
> > +
> > ÂÂÂÂÂ ctx_dbg(3, ctx, "Scanning Port node for csi2 port: %d\n", inst);
> > ÂÂÂÂÂ for (index = 0; index < CAL_NUM_CSI2_PORTS; index++) {
> > ÂÂÂÂÂÂÂÂÂ 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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