linux-kernel - drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_factory.c:384 construct_phy() warn: variable dereferenced before check 'link->link

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Date:   Mon, 22 May 2023 09:47:36 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     oe-kbuild@...ts.linux.dev, Wenjing Liu <wenjing.liu@....com>
Cc:     lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Alex Deucher <alexander.deucher@....com>,
        Jun Lei <Jun.Lei@....com>
Subject: drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_factory.c:384
 construct_phy() warn: variable dereferenced before check 'link->link_enc'
 (see line 381)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   d635f6cc934bcd467c5d67148ece74632fd96abf
commit: 76f5dc40ebb188b081e03783541856c03e97f8e0 drm/amd/display: move dc_link functions in link root folder to dc_link_exports
config: ia64-randconfig-m041-20230514
compiler: ia64-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
| Reported-by: Dan Carpenter <error27@...il.com>
| Closes: https://lore.kernel.org/r/202305201930.FVPVEaPp-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_factory.c:384 construct_phy() warn: variable dereferenced before check 'link->link_enc' (see line 381)

vim +384 drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_factory.c

54618888d1ea7a Wenjing Liu    2023-01-18  367  	enc_init_data.ctx = dc_ctx;
54618888d1ea7a Wenjing Liu    2023-01-18  368  	bp_funcs->get_src_obj(dc_ctx->dc_bios, link->link_id, 0,
54618888d1ea7a Wenjing Liu    2023-01-18  369  			      &enc_init_data.encoder);
54618888d1ea7a Wenjing Liu    2023-01-18  370  	enc_init_data.connector = link->link_id;
54618888d1ea7a Wenjing Liu    2023-01-18  371  	enc_init_data.channel = get_ddc_line(link);
54618888d1ea7a Wenjing Liu    2023-01-18  372  	enc_init_data.hpd_source = get_hpd_line(link);
54618888d1ea7a Wenjing Liu    2023-01-18  373  
54618888d1ea7a Wenjing Liu    2023-01-18  374  	link->hpd_src = enc_init_data.hpd_source;
54618888d1ea7a Wenjing Liu    2023-01-18  375  
54618888d1ea7a Wenjing Liu    2023-01-18  376  	enc_init_data.transmitter =
54618888d1ea7a Wenjing Liu    2023-01-18  377  		translate_encoder_to_transmitter(enc_init_data.encoder);
54618888d1ea7a Wenjing Liu    2023-01-18  378  	link->link_enc =
54618888d1ea7a Wenjing Liu    2023-01-18  379  		link->dc->res_pool->funcs->link_enc_create(dc_ctx, &enc_init_data);
54618888d1ea7a Wenjing Liu    2023-01-18  380  
54618888d1ea7a Wenjing Liu    2023-01-18 @381  	DC_LOG_DC("BIOS object table - DP_IS_USB_C: %d", link->link_enc->features.flags.bits.DP_IS_USB_C);
                                                                                                 ^^^^^^^^^^^^^^^^
Dereference

54618888d1ea7a Wenjing Liu    2023-01-18  382  	DC_LOG_DC("BIOS object table - IS_DP2_CAPABLE: %d", link->link_enc->features.flags.bits.IS_DP2_CAPABLE);
                                                                                                    ^^^^^^^^^^^^^^^^
Here too.

54618888d1ea7a Wenjing Liu    2023-01-18  383  
54618888d1ea7a Wenjing Liu    2023-01-18 @384  	if (!link->link_enc) {
                                                     ^^^^^^^^^^^^^^
NULL checked too late.


54618888d1ea7a Wenjing Liu    2023-01-18  385  		DC_ERROR("Failed to create link encoder!\n");
54618888d1ea7a Wenjing Liu    2023-01-18  386  		goto link_enc_create_fail;
54618888d1ea7a Wenjing Liu    2023-01-18  387  	}
54618888d1ea7a Wenjing Liu    2023-01-18  388  

-- 
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https://github.com/intel/lkp-tests/wiki