[igt-dev] [PATCH i-g-t] lib/igt_device_scan: init card in igt_device_find_first_i915_discrete_card()

[Zbigniew Kempczyński]

On Wed, Sep 30, 2020 at 03:47:56PM -0400, Lyude wrote:
> From: Lyude Paul <lyude at redhat.com>
> 
> Because we never initialize the card pointer passed to
> igt_device_find_first_i915_discrete_card() if we don't match any cards, we make
> the mistake of checking the contents of card in main() in intel_gpu_top.c before
> they've actually been initialized, which can lead to a segfault in some
> scenarios:
> 
>    # intel_gpu_top
>    intel_gpu_top: ../tools/intel_gpu_top.c:1297: tr_pmu_name: Assertion `ret == (bufsize-1)' failed.
>    abort--core dumped
> 
> So, fix it by making sure to initialize card in
> igt_device_find_first_i915_discrete_card() like we do in
> igt_device_card_match().
> 
> Signed-off-by: Lyude Paul <lyude at redhat.com>
> Reported-by: Chris Siebenmann <cks-rhbugzilla at cs.toronto.edu>
> Fedora bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1884016
> ---
>  lib/igt_device_scan.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/lib/igt_device_scan.c b/lib/igt_device_scan.c
> index 345bae76..d77311a4 100644
> --- a/lib/igt_device_scan.c
> +++ b/lib/igt_device_scan.c
> @@ -453,6 +453,8 @@ void igt_device_find_first_i915_discrete_card(struct igt_device_card *card)
>  {
>  	struct igt_device *dev;
>  
> +	memset(card, 0, sizeof(*card));
> +
>  	igt_list_for_each_entry(dev, &igt_devs.all, link) {
>  
>  		if (!is_pci_subsystem(dev))
> -- 

Maybe this function should return boolean does card was found or not?
This will require change in intel_gpu_top and check return value
but is more intuitive and appropriate message can be show that card
is not found.

--
Zbigniew


> 2.26.2
> 
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