linux-kernel - drivers/gpu/drm/i915/display/intel_ddi.c:4030 intel_ddi_encoder_destroy() warn: variable dereferenced before check 'dig

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Date:   Tue, 28 Sep 2021 09:27:53 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Imre Deak <imre.deak@...el.com>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: drivers/gpu/drm/i915/display/intel_ddi.c:4030
 intel_ddi_encoder_destroy() warn: variable dereferenced before check
 'dig_port' (see line 4022)

tree:   https://github.com/0day-ci/linux/commits/Imre-Deak/drm-i915-tc-Fix-TypeC-connect-disconnect-sequences/20210922-114722
head:   b4b1e126eb50a8a27bb1348ad13dae05e299a9ac
commit: 295fc54769b7afb65114732f61b1448c3e693011 drm/i915/tc: Fix TypeC PHY connect/disconnect logic on ADL-P
config: x86_64-randconfig-m001-20210927 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

smatch warnings:
drivers/gpu/drm/i915/display/intel_ddi.c:4030 intel_ddi_encoder_destroy() warn: variable dereferenced before check 'dig_port' (see line 4022)

vim +/dig_port +4030 drivers/gpu/drm/i915/display/intel_ddi.c

f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4018  static void intel_ddi_encoder_destroy(struct drm_encoder *encoder)
f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4019  {
4a300e65b59b66 drivers/gpu/drm/i915/display/intel_ddi.c Imre Deak      2021-05-26  4020  	struct drm_i915_private *i915 = to_i915(encoder->dev);
b7d02c3a124d9b drivers/gpu/drm/i915/display/intel_ddi.c Ville Syrjälä  2019-12-04  4021  	struct intel_digital_port *dig_port = enc_to_dig_port(to_intel_encoder(encoder));
295fc54769b7af drivers/gpu/drm/i915/display/intel_ddi.c Imre Deak      2021-09-21 @4022  	enum phy phy = intel_port_to_phy(i915, dig_port->base.port);
                                                                                                                                       ^^^^^^^^^^^^^^^^^^^
Dereference.

f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4023  
f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4024  	intel_dp_encoder_flush_work(encoder);
295fc54769b7af drivers/gpu/drm/i915/display/intel_ddi.c Imre Deak      2021-09-21  4025  	if (intel_phy_is_tc(i915, phy))
295fc54769b7af drivers/gpu/drm/i915/display/intel_ddi.c Imre Deak      2021-09-21  4026  		intel_tc_port_flush_work(dig_port);
4a300e65b59b66 drivers/gpu/drm/i915/display/intel_ddi.c Imre Deak      2021-05-26  4027  	intel_display_power_flush_work(i915);
f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4028  
f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4029  	drm_encoder_cleanup(encoder);
a6c6eac947d519 drivers/gpu/drm/i915/display/intel_ddi.c Anshuman Gupta 2021-01-11 @4030  	if (dig_port)
                                                                                                    ^^^^^^^^
Checked too late.

a6c6eac947d519 drivers/gpu/drm/i915/display/intel_ddi.c Anshuman Gupta 2021-01-11  4031  		kfree(dig_port->hdcp_port_data.streams);
f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4032  	kfree(dig_port);
f6bff60e927b2f drivers/gpu/drm/i915/intel_ddi.c         Imre Deak      2018-12-14  4033  }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org