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Message-ID: <YfPCyxqO5zQWv8Xn@kroah.com>
Date: Fri, 28 Jan 2022 11:17:47 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Zhou Qingyang <zhou1615@....edu>
Cc: kjlu@....edu, Harry Wentland <harry.wentland@....com>,
Leo Li <sunpeng.li@....com>,
Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
"Pan, Xinhui" <Xinhui.Pan@....com>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
Qingqing Zhuo <qingqing.zhuo@....com>,
Jude Shih <shenshih@....com>,
Aurabindo Pillai <aurabindo.pillai@....com>,
Nikola Cornij <nikola.cornij@....com>,
Wayne Lin <Wayne.Lin@....com>, Roman Li <Roman.Li@....com>,
Tony Cheng <Tony.Cheng@....com>, amd-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: Fix a NULL pointer dereference in
amdgpu_dm_connector_add_common_modes()
On Tue, Jan 25, 2022 at 12:57:29AM +0800, Zhou Qingyang wrote:
> In amdgpu_dm_connector_add_common_modes(), amdgpu_dm_create_common_mode()
> is assigned to mode and is passed to drm_mode_probed_add() directly after
> that. drm_mode_probed_add() passes &mode->head to list_add_tail(), and
> there is a dereference of it in list_add_tail() without recoveries, which
> could lead to NULL pointer dereference on failure of
> amdgpu_dm_create_common_mode().
>
> Fix this by adding a NULL check of mode.
>
> This bug was found by a static analyzer.
>
> Builds with 'make allyesconfig' show no new warnings,
> and our static analyzer no longer warns about this code.
>
> Fixes: e7b07ceef2a6 ("drm/amd/display: Merge amdgpu_dm_types and amdgpu_dm")
> Signed-off-by: Zhou Qingyang <zhou1615@....edu>
> ---
> The analysis employs differential checking to identify inconsistent
> security operations (e.g., checks or kfrees) between two code paths
> and confirms that the inconsistent operations are not recovered in the
> current function or the callers, so they constitute bugs.
>
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
>
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 7f9773f8dab6..9ad94186b146 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -8143,6 +8143,9 @@ static void amdgpu_dm_connector_add_common_modes(struct drm_encoder *encoder,
> mode = amdgpu_dm_create_common_mode(encoder,
> common_modes[i].name, common_modes[i].w,
> common_modes[i].h);
> + if (!mode)
> + continue;
> +
> drm_mode_probed_add(connector, mode);
> amdgpu_dm_connector->num_modes++;
> }
> --
> 2.25.1
>
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