linux-kernel - Re: drivers/gpu/drm/msm/dp/dp_debug.c:218 dp_debug_init() warn: passing zero to 'PTR

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Message-ID: <cb25d69c78e9bb754bd76701c9253f44@codeaurora.org>
Date:   Wed, 03 Mar 2021 16:27:12 -0800
From:   abhinavk@...eaurora.org
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     kbuild@...ts.01.org, lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Rob Clark <robdclark@...omium.org>
Subject: Re: drivers/gpu/drm/msm/dp/dp_debug.c:218 dp_debug_init() warn:
 passing zero to 'PTR_ERR'

Hi Dan

Thanks for reporting this, will submit a change to fix this.

Abhinav

On 2021-02-28 23:14, Dan Carpenter wrote:
> tree:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> master
> head:   fe07bfda2fb9cdef8a4d4008a409bb02f35f1bd8
> commit: d11a93690df7e9a7e07c0784ecad019a627b1449 drm/msm/dp: add
> debugfs support to DP driver
> config: arm64-randconfig-m031-20210301 (attached as .config)
> compiler: aarch64-linux-gcc (GCC) 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>
> 
> New smatch warnings:
> drivers/gpu/drm/msm/dp/dp_debug.c:218 dp_debug_init() warn: passing
> zero to 'PTR_ERR'
> 
> Old smatch warnings:
> drivers/gpu/drm/msm/dp/dp_debug.c:227 dp_debug_init() warn: passing
> zero to 'PTR_ERR'
> 
> vim +/PTR_ERR +218 drivers/gpu/drm/msm/dp/dp_debug.c
> 
> d11a93690df7e9 Abhinav Kumar 2020-09-12  209  static int
> dp_debug_init(struct dp_debug *dp_debug)
> d11a93690df7e9 Abhinav Kumar 2020-09-12  210  {
> d11a93690df7e9 Abhinav Kumar 2020-09-12  211  	int rc = 0;
> d11a93690df7e9 Abhinav Kumar 2020-09-12  212  	struct dp_debug_private
> *debug = container_of(dp_debug,
> d11a93690df7e9 Abhinav Kumar 2020-09-12  213  			struct
> dp_debug_private, dp_debug);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  214  	struct dentry *dir, 
> *file;
> d11a93690df7e9 Abhinav Kumar 2020-09-12  215
> d11a93690df7e9 Abhinav Kumar 2020-09-12  216  	dir =
> debugfs_create_dir(DEBUG_NAME, NULL);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  217  	if (IS_ERR_OR_NULL(dir)) 
> {
> d11a93690df7e9 Abhinav Kumar 2020-09-12 @218  		rc = PTR_ERR(dir);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  219  		DRM_ERROR("[%s]
> debugfs create dir failed, rc = %d\n",
> d11a93690df7e9 Abhinav Kumar 2020-09-12  220  				  DEBUG_NAME, rc);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  221  		goto error;
> 
> Debugfs function never return NULL, but actually debugfs functions
> aren't supposed to be checked in the normal case (the abnormal case is
> where you are trying to dereference "dir" and "file" within the driver
> itself, so it doesn't apply here).
> 
> So then the function becomes a lot simpler, if it's written in the
> canonical way.  This should probably be documented better in the
> Documentation/filesystems/debugfs.rst file...  :/
> 
> static void dp_debug_init(struct dp_debug *dp_debug)
> {
> 	struct dp_debug_private *debug = container_of(dp_debug,
> 						      struct dp_debug_private, dp_debug);
> 
> 	debug->root = debugfs_create_dir(DEBUG_NAME, NULL);
> 	debugfs_create_file("dp_debug", 0444, dir, debug, &dp_debug_fops);
> }
> 
> d11a93690df7e9 Abhinav Kumar 2020-09-12  222  	}
> d11a93690df7e9 Abhinav Kumar 2020-09-12  223
> d11a93690df7e9 Abhinav Kumar 2020-09-12  224  	file =
> debugfs_create_file("dp_debug", 0444, dir,
> d11a93690df7e9 Abhinav Kumar 2020-09-12  225  			debug, 
> &dp_debug_fops);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  226  	if 
> (IS_ERR_OR_NULL(file)) {
> d11a93690df7e9 Abhinav Kumar 2020-09-12  227  		rc = PTR_ERR(file);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  228  		DRM_ERROR("[%s]
> debugfs create file failed, rc=%d\n",
> d11a93690df7e9 Abhinav Kumar 2020-09-12  229  				  DEBUG_NAME, rc);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  230  		goto error_remove_dir;
> d11a93690df7e9 Abhinav Kumar 2020-09-12  231  	}
> d11a93690df7e9 Abhinav Kumar 2020-09-12  232
> d11a93690df7e9 Abhinav Kumar 2020-09-12  233  	debug->root = dir;
> d11a93690df7e9 Abhinav Kumar 2020-09-12  234  	return rc;
> d11a93690df7e9 Abhinav Kumar 2020-09-12  235   error_remove_dir:
> d11a93690df7e9 Abhinav Kumar 2020-09-12  236  	debugfs_remove(dir);
> d11a93690df7e9 Abhinav Kumar 2020-09-12  237   error:
> d11a93690df7e9 Abhinav Kumar 2020-09-12  238  	return rc;
> d11a93690df7e9 Abhinav Kumar 2020-09-12  239  }
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org