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

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Message-ID: <20210301071431.GO2087@kadam>
Date:   Mon, 1 Mar 2021 10:14:31 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Abhinav Kumar <abhinavk@...eaurora.org>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Rob Clark <robdclark@...omium.org>
Subject: drivers/gpu/drm/msm/dp/dp_debug.c:218 dp_debug_init() warn: passing
 zero to 'PTR_ERR'

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  }

---
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https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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