linux-kernel - Re: [PATCH 1/3] drm/connector: hdmi: Fix memory leak in drm_display_mode_from_cea

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Message-ID: <20241014-fervent-whimsical-oyster-b0926d@houat>
Date: Mon, 14 Oct 2024 11:11:26 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, 
	airlied@...il.com, simona@...ll.ch, christian.koenig@....com, ray.huang@....com, 
	dmitry.baryshkov@...aro.org, dave.stevenson@...pberrypi.com, mcanal@...lia.com, 
	quic_jjohnson@...cinc.com, karolina.stolarek@...el.com, Arunpravin.PaneerSelvam@....com, 
	thomas.hellstrom@...ux.intel.com, asomalap@....com, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/connector: hdmi: Fix memory leak in
 drm_display_mode_from_cea_vic()

On Mon, Oct 14, 2024 at 03:16:30PM GMT, Jinjie Ruan wrote:
> modprobe drm_connector_test and then rmmod drm_connector_test,
> the following memory leak occurs.
> 
> The `mode` allocated in drm_mode_duplicate() called by
> drm_display_mode_from_cea_vic() is not freed, which cause the memory leak:
> 
> 	unreferenced object 0xffffff80cb0ee400 (size 128):
> 	  comm "kunit_try_catch", pid 1948, jiffies 4294950339
> 	  hex dump (first 32 bytes):
> 	    14 44 02 00 80 07 d8 07 04 08 98 08 00 00 38 04  .D............8.
> 	    3c 04 41 04 65 04 00 00 05 00 00 00 00 00 00 00  <.A.e...........
> 	  backtrace (crc 90e9585c):
> 	    [<00000000ec42e3d7>] kmemleak_alloc+0x34/0x40
> 	    [<00000000d0ef055a>] __kmalloc_cache_noprof+0x26c/0x2f4
> 	    [<00000000c2062161>] drm_mode_duplicate+0x44/0x19c
> 	    [<00000000f96c74aa>] drm_display_mode_from_cea_vic+0x88/0x98
> 	    [<00000000d8f2c8b4>] 0xffffffdc982a4868
> 	    [<000000005d164dbc>] kunit_try_run_case+0x13c/0x3ac
> 	    [<000000006fb23398>] kunit_generic_run_threadfn_adapter+0x80/0xec
> 	    [<000000006ea56ca0>] kthread+0x2e8/0x374
> 	    [<000000000676063f>] ret_from_fork+0x10/0x20
> 	......
> 
> Free `mode` by calling drm_mode_destroy() to fix it.
> 
> Cc: stable@...r.kernel.org
> Fixes: abb6f74973e2 ("drm/tests: Add HDMI TDMS character rate tests")
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
>  drivers/gpu/drm/tests/drm_connector_test.c | 24 ++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tests/drm_connector_test.c b/drivers/gpu/drm/tests/drm_connector_test.c
> index 15e36a8db685..9c94d26b3486 100644
> --- a/drivers/gpu/drm/tests/drm_connector_test.c
> +++ b/drivers/gpu/drm/tests/drm_connector_test.c
> @@ -1004,6 +1004,8 @@ static void drm_test_drm_hdmi_compute_mode_clock_rgb(struct kunit *test)
>  	rate = drm_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_RGB);
>  	KUNIT_ASSERT_GT(test, rate, 0);
>  	KUNIT_EXPECT_EQ(test, mode->clock * 1000ULL, rate);
> +
> +	drm_mode_destroy(drm, mode);
>  }

If KUNIT_ASSERT_GT triggers, then we would end up leaking the mode as well.

I think we should create a kunit_drm_display_mode_from_cea_vic()
function that registers a kunit action to free the mode when the test is
done.

Maxime

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