drivers/gpu/drm/nouveau/nouveau_dp.c:237 nouveau_dp_irq() warn: variable dereferenced before check 'outp' (see line 232)

[Dan Carpenter]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   815fb87b753055df2d9e50f6cd80eb10235fe3e9
commit: 773eb04d14a11552b2c3953097ed09cde2ab4831 drm/nouveau/disp: expose conn event class
config: i386-randconfig-141-20231105 (https://download.01.org/0day-ci/archive/20231202/202312021916.U9nxtVaD-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231202/202312021916.U9nxtVaD-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
| Closes: https://lore.kernel.org/r/202312021916.U9nxtVaD-lkp@xxxxxxxxx/

smatch warnings:
drivers/gpu/drm/nouveau/nouveau_dp.c:237 nouveau_dp_irq() warn: variable dereferenced before check 'outp' (see line 232)

vim +/outp +237 drivers/gpu/drm/nouveau/nouveau_dp.c

773eb04d14a115 Ben Skeggs 2022-06-01  225  void
773eb04d14a115 Ben Skeggs 2022-06-01  226  nouveau_dp_irq(struct work_struct *work)
a0922278f83eae Lyude Paul 2020-08-26  227  {
773eb04d14a115 Ben Skeggs 2022-06-01  228  	struct nouveau_connector *nv_connector =
773eb04d14a115 Ben Skeggs 2022-06-01  229  		container_of(work, typeof(*nv_connector), irq_work);
a0922278f83eae Lyude Paul 2020-08-26  230  	struct drm_connector *connector = &nv_connector->base;
a0922278f83eae Lyude Paul 2020-08-26  231  	struct nouveau_encoder *outp = find_encoder(connector, DCB_OUTPUT_DP);
773eb04d14a115 Ben Skeggs 2022-06-01 @232  	struct nouveau_drm *drm = nouveau_drm(outp->base.base.dev);
                                                                                      ^^^^^^
Dereference

a0922278f83eae Lyude Paul 2020-08-26  233  	struct nv50_mstm *mstm;
016dacb60e6d4b Ben Skeggs 2022-06-01  234  	u64 hpd = 0;
a4efad354cf1b9 Lyude Paul 2020-08-26  235  	int ret;
a0922278f83eae Lyude Paul 2020-08-26  236  
a0922278f83eae Lyude Paul 2020-08-26 @237  	if (!outp)
                                                    ^^^^^
Too late.

a0922278f83eae Lyude Paul 2020-08-26  238  		return;
a0922278f83eae Lyude Paul 2020-08-26  239  
a0922278f83eae Lyude Paul 2020-08-26  240  	mstm = outp->dp.mstm;
a0922278f83eae Lyude Paul 2020-08-26  241  	NV_DEBUG(drm, "service %s\n", connector->name);
a0922278f83eae Lyude Paul 2020-08-26  242  
a0922278f83eae Lyude Paul 2020-08-26  243  	mutex_lock(&outp->dp.hpd_irq_lock);
a0922278f83eae Lyude Paul 2020-08-26  244  
a0922278f83eae Lyude Paul 2020-08-26  245  	if (mstm && mstm->is_mst) {
a0922278f83eae Lyude Paul 2020-08-26  246  		if (!nv50_mstm_service(drm, nv_connector, mstm))
773eb04d14a115 Ben Skeggs 2022-06-01  247  			hpd |= NVIF_CONN_EVENT_V0_UNPLUG;

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