linux-kernel - Re: security/loadpin/loadpin.c:365 dm_verity_ioctl() warn: maybe return -EFAULT instead of the bytes remaining?

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Date:   Tue, 16 Aug 2022 12:17:57 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     kbuild@...ts.01.org, Matthias Kaehlcke <mka@...omium.org>,
        lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: security/loadpin/loadpin.c:365 dm_verity_ioctl() warn: maybe
 return -EFAULT instead of the bytes remaining?

On Mon, Aug 15, 2022 at 11:07:12AM +0300, Dan Carpenter wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   aea23e7c464bfdec04b52cf61edb62030e9e0d0a
> commit: 3f805f8cc23ba35679dd01446929292911c2b469 LoadPin: Enable loading from trusted dm-verity devices
> config: s390-randconfig-m031-20220810 (https://download.01.org/0day-ci/archive/20220814/202208141119.RKGSGoZ7-lkp@intel.com/config)
> compiler: s390-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:
> security/loadpin/loadpin.c:365 dm_verity_ioctl() warn: maybe return -EFAULT instead of the bytes remaining?
> 
> vim +365 security/loadpin/loadpin.c
> 
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  355  static long dm_verity_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  356  {
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  357  	void __user *uarg = (void __user *)arg;
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  358  	unsigned int fd;
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  359  	int rc;
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  360  
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  361  	switch (cmd) {
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  362  	case LOADPIN_IOC_SET_TRUSTED_VERITY_DIGESTS:
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  363  		rc = copy_from_user(&fd, uarg, sizeof(fd));
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  364  		if (rc)
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27 @365  			return rc;
> 
> The copy_from_user() function returns the number of bytes remaining to
> be copied.  It should be:
> 
> 	if (copy_from_user(&fd, uarg, sizeof(fd)))
> 		return -EFAULT;

Oops, yes. I'll get this fixed.

-Kees

> 
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  366  
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  367  		return read_trusted_verity_root_digests(fd);
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  368  
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  369  	default:
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  370  		return -EINVAL;
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  371  	}
> 3f805f8cc23ba3 Matthias Kaehlcke 2022-06-27  372  }
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://01.org/lkp
> 

-- 
Kees Cook