Re: fs/proc/vmcore.c:161:34: sparse: sparse: incorrect type in argument 1 (different address spaces)

[David Hildenbrand <david@redhat.com>]

On 24.11.21 16:42, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   5d9f4cf36721aba199975a9be7863a3ff5cd4b59
> commit: c1e63117711977cc4295b2ce73de29dd17066c82 proc/vmcore: fix clearing user buffer by properly using clear_user()
> date:   4 days ago
> config: ia64-allyesconfig (https://download.01.org/0day-ci/archive/20211124/202111242331.x19Qywph-lkp@intel.com/config)
> compiler: ia64-linux-gcc (GCC) 11.2.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # apt-get install sparse
>         # sparse version: v0.6.4-dirty
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c1e63117711977cc4295b2ce73de29dd17066c82
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout c1e63117711977cc4295b2ce73de29dd17066c82
>         # save the config file to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=ia64 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> 
> sparse warnings: (new ones prefixed by >>)
>>> fs/proc/vmcore.c:161:34: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void const [noderef] __user *p @@     got char *buf @@
>    fs/proc/vmcore.c:161:34: sparse:     expected void const [noderef] __user *p
>    fs/proc/vmcore.c:161:34: sparse:     got char *buf
>>> fs/proc/vmcore.c:161:34: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void [noderef] __user * @@     got char *buf @@
>    fs/proc/vmcore.c:161:34: sparse:     expected void [noderef] __user *
>    fs/proc/vmcore.c:161:34: sparse:     got char *buf
> 
> vim +161 fs/proc/vmcore.c
> 
>    133	
>    134	/* Reads a page from the oldmem device from given offset. */
>    135	ssize_t read_from_oldmem(char *buf, size_t count,
>    136				 u64 *ppos, int userbuf,
>    137				 bool encrypted)
>    138	{
>    139		unsigned long pfn, offset;
>    140		size_t nr_bytes;
>    141		ssize_t read = 0, tmp;
>    142	
>    143		if (!count)
>    144			return 0;
>    145	
>    146		offset = (unsigned long)(*ppos % PAGE_SIZE);
>    147		pfn = (unsigned long)(*ppos / PAGE_SIZE);
>    148	
>    149		down_read(&vmcore_cb_rwsem);
>    150		do {
>    151			if (count > (PAGE_SIZE - offset))
>    152				nr_bytes = PAGE_SIZE - offset;
>    153			else
>    154				nr_bytes = count;
>    155	
>    156			/* If pfn is not ram, return zeros for sparse dump files */
>    157			if (!pfn_is_ram(pfn)) {
>    158				tmp = 0;
>    159				if (!userbuf)
>    160					memset(buf, 0, nr_bytes);
>  > 161				else if (clear_user(buf, nr_bytes))
>    162					tmp = -EFAULT;
>    163			} else {
>    164				if (encrypted)
>    165					tmp = copy_oldmem_page_encrypted(pfn, buf,
>    166									 nr_bytes,
>    167									 offset,
>    168									 userbuf);
>    169				else
>    170					tmp = copy_oldmem_page(pfn, buf, nr_bytes,
>    171							       offset, userbuf);
>    172			}
>    173			if (tmp < 0) {
>    174				up_read(&vmcore_cb_rwsem);
>    175				return tmp;
>    176			}
>    177	
>    178			*ppos += nr_bytes;
>    179			count -= nr_bytes;
>    180			buf += nr_bytes;
>    181			read += nr_bytes;
>    182			++pfn;
>    183			offset = 0;
>    184		} while (count);
>    185	
>    186		up_read(&vmcore_cb_rwsem);
>    187		return read;
>    188	}
>    189	

Sparse is wrong as it doesn't see the bigger picture. "int userbuf"
tells us what we're actually dealing with ...


-- 
Thanks,

David / dhildenb