linux-kernel - drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c:395 dc_stream_set_cursor_position() warn: variable dereferenced before check 'stream' (see line 392)

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Message-ID: <202210260950.kMcetJwT-lkp@intel.com>
Date:   Thu, 27 Oct 2022 10:36:05 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Alvin Lee <Alvin.Lee2@....com>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        Alex Deucher <alexander.deucher@....com>,
        Samson Tam <Samson.Tam@....com>
Subject: drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c:395
 dc_stream_set_cursor_position() warn: variable dereferenced before check
 'stream' (see line 392)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   4dc12f37a8e98e1dca5521c14625c869537b50b6
commit: a141d2083b462505727e14d98db5fc3cd43d59c6 drm/amd/display: Add debug option for exiting idle optimizations on cursor updates
config: mips-randconfig-m031-20221018
compiler: mips64el-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 <dan.carpenter@...cle.com>

smatch warnings:
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c:395 dc_stream_set_cursor_position() warn: variable dereferenced before check 'stream' (see line 392)

vim +/stream +395 drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c

ab2541b6739508 Aric Cyr            2016-12-29  388  bool dc_stream_set_cursor_position(
0971c40e180696 Harry Wentland      2017-07-27  389  	struct dc_stream_state *stream,
beb16b6a0f921f Dmytro Laktyushkin  2017-04-21  390  	const struct dc_cursor_position *position)
ab2541b6739508 Aric Cyr            2016-12-29  391  {
a141d2083b4625 Alvin Lee           2022-06-03 @392  	struct dc  *dc = stream->ctx->dc;
                                                                         ^^^^^^^^^^^^^^^^
New unchecked dereference

4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  393  	bool reset_idle_optimizations = false;
ab2541b6739508 Aric Cyr            2016-12-29  394  
4fa086b9b66408 Leo (Sunpeng  Li    2017-07-25 @395) 	if (NULL == stream) {
                                                            ^^^^^^^^^^^^^^
Old Yoda code check for NULL

ab2541b6739508 Aric Cyr            2016-12-29  396  		dm_error("DC: dc_stream is NULL!\n");
ab2541b6739508 Aric Cyr            2016-12-29  397  		return false;
ab2541b6739508 Aric Cyr            2016-12-29  398  	}
ab2541b6739508 Aric Cyr            2016-12-29  399  
ab2541b6739508 Aric Cyr            2016-12-29  400  	if (NULL == position) {
ab2541b6739508 Aric Cyr            2016-12-29  401  		dm_error("DC: cursor position is NULL!\n");
ab2541b6739508 Aric Cyr            2016-12-29  402  		return false;
ab2541b6739508 Aric Cyr            2016-12-29  403  	}
ab2541b6739508 Aric Cyr            2016-12-29  404  
2b77dcc5e5aa38 Anthony Koo         2019-11-05  405  	dc = stream->ctx->dc;
bae1f0b8a5b189 Nicholas Kazlauskas 2021-05-19  406  	dc_z10_restore(dc);
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  407  
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  408  	/* disable idle optimizations if enabling cursor */
a141d2083b4625 Alvin Lee           2022-06-03  409  	if (dc->idle_optimizations_allowed && (!stream->cursor_position.enable || dc->debug.exit_idle_opt_for_cursor_updates)
a141d2083b4625 Alvin Lee           2022-06-03  410  			&& position->enable) {
4b675aad969507 Joshua Aberback     2020-08-31  411  		dc_allow_idle_optimizations(dc, false);
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  412  		reset_idle_optimizations = true;
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  413  	}
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  414  
33fd17d9125c00 Eric Yang           2018-01-18  415  	stream->cursor_position = *position;
ab2541b6739508 Aric Cyr            2016-12-29  416  
4fd771ea441ed9 Roy Chan            2021-07-19  417  	program_cursor_position(dc, stream, position);
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  418  	/* re-enable idle optimizations if necessary */
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  419  	if (reset_idle_optimizations)
4b675aad969507 Joshua Aberback     2020-08-31  420  		dc_allow_idle_optimizations(dc, true);
4d55b0dd1cdd85 Bhawanpreet Lakha   2020-05-21  421  
beb16b6a0f921f Dmytro Laktyushkin  2017-04-21  422  	return true;
ab2541b6739508 Aric Cyr            2016-12-29  423  }

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