Re: [PATCH v3 18/22] mm/mshare: Add an ioctl for mapping objects in an mshare region

[kernel test robot <lkp@intel.com>]

Hi Anthony,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on next-20250820]
[cannot apply to tip/sched/core trace/for-next tip/x86/core tip/x86/mm kees/for-next/execve linus/master v6.17-rc2]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Anthony-Yznaga/mm-Add-msharefs-filesystem/20250820-091021
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250820010415.699353-19-anthony.yznaga%40oracle.com
patch subject: [PATCH v3 18/22] mm/mshare: Add an ioctl for mapping objects in an mshare region
config: x86_64-allyesconfig (https://download.01.org/0day-ci/archive/20250821/202508210437.BXbf4eok-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250821/202508210437.BXbf4eok-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508210437.BXbf4eok-lkp@intel.com/

All warnings (new ones prefixed by >>):

   mm/mshare.c:305:16: warning: variable 'mshare_start' set but not used [-Wunused-but-set-variable]
     305 |         unsigned long mshare_start, mshare_size;
         |                       ^
>> mm/mshare.c:386:57: warning: variable 'vm_flags' is uninitialized when used here [-Wuninitialized]
     386 |         mapped_addr = __do_mmap(NULL, addr, size, prot, flags, vm_flags,
         |                                                                ^~~~~~~~
   mm/mshare.c:361:21: note: initialize the variable 'vm_flags' to silence this warning
     361 |         vm_flags_t vm_flags;
         |                            ^
         |                             = 0
   2 warnings generated.


vim +/vm_flags +386 mm/mshare.c

   297	
   298	static unsigned long
   299	msharefs_get_unmapped_area(struct file *file, unsigned long addr,
   300			unsigned long len, unsigned long pgoff, unsigned long flags)
   301	{
   302		struct mshare_data *m_data = file->private_data;
   303		struct mm_struct *mm = current->mm;
   304		struct vm_area_struct *vma, *prev;
 > 305		unsigned long mshare_start, mshare_size;
   306		const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
   307	
   308		mmap_assert_write_locked(mm);
   309	
   310		if ((flags & MAP_TYPE) == MAP_PRIVATE)
   311			return -EINVAL;
   312	
   313		if (!mshare_is_initialized(m_data) || !mshare_has_owner(m_data))
   314			return -EINVAL;
   315	
   316		mshare_start = m_data->start;
   317		mshare_size = m_data->size;
   318	
   319		if (len != mshare_size)
   320			return -EINVAL;
   321	
   322		if (len > mmap_end - mmap_min_addr)
   323			return -ENOMEM;
   324	
   325		if (flags & MAP_FIXED) {
   326			if (!IS_ALIGNED(addr, mshare_align))
   327				return -EINVAL;
   328			return addr;
   329		}
   330	
   331		if (addr) {
   332			addr = ALIGN(addr, mshare_align);
   333			vma = find_vma_prev(mm, addr, &prev);
   334			if (mmap_end - len >= addr && addr >= mmap_min_addr &&
   335			    (!vma || addr + len <= vm_start_gap(vma)) &&
   336			    (!prev || addr >= vm_end_gap(prev)))
   337				return addr;
   338		}
   339	
   340		if (!mm_flags_test(MMF_TOPDOWN, mm))
   341			return msharefs_get_unmapped_area_bottomup(file, addr, len,
   342					pgoff, flags);
   343		else
   344			return msharefs_get_unmapped_area_topdown(file, addr, len,
   345					pgoff, flags);
   346	}
   347	
   348	static long
   349	msharefs_create_mapping(struct mshare_data *m_data, struct mshare_create *mcreate)
   350	{
   351		struct mm_struct *host_mm = m_data->mm;
   352		unsigned long mshare_start, mshare_end;
   353		unsigned long region_offset = mcreate->region_offset;
   354		unsigned long size = mcreate->size;
   355		unsigned int fd = mcreate->fd;
   356		int flags = mcreate->flags;
   357		int prot = mcreate->prot;
   358		unsigned long populate = 0;
   359		unsigned long mapped_addr;
   360		unsigned long addr;
   361		vm_flags_t vm_flags;
   362		int error = -EINVAL;
   363	
   364		mshare_start = m_data->start;
   365		mshare_end = mshare_start + m_data->size;
   366		addr = mshare_start + region_offset;
   367	
   368		if ((addr < mshare_start) || (addr >= mshare_end) ||
   369		    (addr + size > mshare_end))
   370			goto out;
   371	
   372		/*
   373		 * Only anonymous shared memory at fixed addresses is allowed for now.
   374		 */
   375		if ((flags & (MAP_SHARED | MAP_FIXED)) != (MAP_SHARED | MAP_FIXED))
   376			goto out;
   377		if (fd != -1)
   378			goto out;
   379	
   380		if (mmap_write_lock_killable(host_mm)) {
   381			error = -EINTR;
   382			goto out;
   383		}
   384	
   385		error = 0;
 > 386		mapped_addr = __do_mmap(NULL, addr, size, prot, flags, vm_flags,
   387					0, &populate, NULL, host_mm);
   388	
   389		if (IS_ERR_VALUE(mapped_addr))
   390			error = (long)mapped_addr;
   391	
   392		mmap_write_unlock(host_mm);
   393	out:
   394		return error;
   395	}
   396	

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