Re: [PATCH] vhost: new vhost_vdpa SET/GET_BACKEND_FEATURES handlers

[Dan Carpenter <dan.carpenter@oracle.com>]

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Hi Zhu,

url:    https://github.com/0day-ci/linux/commits/Zhu-Lingshan/vhost-new-vhost_vdpa-SET-GET_BACKEND_FEATURES-handlers/20200909-115726
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next
config: parisc-randconfig-m031-20200909 (attached as .config)
compiler: hppa-linux-gcc (GCC) 9.3.0

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

New smatch warnings:
drivers/vhost/vdpa.c:356 vhost_vdpa_get_backend_features() warn: maybe return -EFAULT instead of the bytes remaining?

# https://github.com/0day-ci/linux/commit/f2da8fc35b4ef003de7d559a8c7730fedf9926f8
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Zhu-Lingshan/vhost-new-vhost_vdpa-SET-GET_BACKEND_FEATURES-handlers/20200909-115726
git checkout f2da8fc35b4ef003de7d559a8c7730fedf9926f8
vim +356 drivers/vhost/vdpa.c

f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  348  static long vhost_vdpa_get_backend_features(void __user *argp)
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  349  {
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  350  	u64 features = VHOST_VDPA_BACKEND_FEATURES;
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  351  	u64 __user *featurep = argp;
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  352  	long r;
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  353  
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  354  	r = copy_to_user(featurep, &features, sizeof(features));
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  355  
f2da8fc35b4ef0 Zhu Lingshan 2020-09-09 @356  	return r;

copy_to_user() returns the number of bytes remaining.  I haven't looked
at how this is called but it should probably return negative error codes
on error:

	if (copy_to_user(featurep, &features, sizeof(features)))
		return -EFAULT;

	return 0;

f2da8fc35b4ef0 Zhu Lingshan 2020-09-09  357  }

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

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