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    Subject[PATCH 5.16 0429/1017] drm/amd/display: Fix a NULL pointer dereference in amdgpu_dm_connector_add_common_modes()
    Date
    From: Zhou Qingyang <zhou1615@umn.edu>

    [ Upstream commit 588a70177df3b1777484267584ef38ab2ca899a2 ]

    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@umn.edu>
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 7a5bb5a3456a..0ec8051cdfb4 100644
    --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
    +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
    @@ -8030,6 +8030,9 @@ 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++;
    }
    --
    2.34.1


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