[akpm-mm:mm-nonmm-unstable 130/151] fs/squashfs/namei.c:141:21: sparse: sparse: unsigned value that used to be signed checked against zero?

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-nonmm-unstable
head:   152f0559e66c079f717de375f133ff127afb1f58
commit: 4dddf794b08bef04e5634dd4b52775a160d2cb6c [130/151] Squashfs: sanity check directory metadata block location
config: sh-randconfig-r2307-20261113 (https://download.01.org/0day-ci/archive/20261113/202611131605.L4Uvbf8p-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 16.2.0
sparse: v0.6.5-rc1-21-g84ec0658
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261113/202611131605.L4Uvbf8p-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/202611131605.L4Uvbf8p-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> fs/squashfs/namei.c:141:21: sparse: sparse: unsigned value that used to be signed checked against zero?
   fs/squashfs/namei.c: note: in included file:
   fs/squashfs/squashfs_helpers.h:79:24: sparse: signed value source

vim +141 fs/squashfs/namei.c

   123	
   124	
   125	static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry,
   126					 unsigned int flags)
   127	{
   128		const unsigned char *name = dentry->d_name.name;
   129		int len = dentry->d_name.len;
   130		struct inode *inode = NULL;
   131		struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info;
   132		struct squashfs_dir_header dirh;
   133		struct squashfs_dir_entry *dire = NULL;
   134		u64 block = squashfs_dir_start(squashfs_i(dir)->start, msblk);
   135		int offset = squashfs_i(dir)->offset;
   136		int err, length;
   137		unsigned int dir_count, size;
   138	
   139		TRACE("Entered squashfs_lookup [%llx:%x]\n", squashfs_i(dir)->start, offset);
   140	
 > 141		if (block < 0)
   142			goto data_error;
   143	
   144		dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
   145		if (dire == NULL) {
   146			ERROR("Failed to allocate squashfs_dir_entry\n");
   147			return ERR_PTR(-ENOMEM);
   148		}
   149	
   150		if (len > SQUASHFS_NAME_LEN) {
   151			err = -ENAMETOOLONG;
   152			goto failed;
   153		}
   154	
   155		length = get_dir_index_using_name(dir->i_sb, &block, &offset,
   156					squashfs_i(dir)->dir_idx_start,
   157					squashfs_i(dir)->dir_idx_offset,
   158					squashfs_i(dir)->dir_idx_cnt, name);
   159	
   160		while (length < i_size_read(dir)) {
   161			/*
   162			 * Read directory header.
   163			 */
   164			err = squashfs_read_metadata(dir->i_sb, &dirh, &block,
   165					&offset, sizeof(dirh));
   166			if (err < 0)
   167				goto read_failure;
   168	
   169			length += sizeof(dirh);
   170	
   171			dir_count = le32_to_cpu(dirh.count) + 1;
   172	
   173			if (dir_count > SQUASHFS_DIR_COUNT)
   174				goto data_error;
   175	
   176			while (dir_count--) {
   177				/*
   178				 * Read directory entry.
   179				 */
   180				err = squashfs_read_metadata(dir->i_sb, dire, &block,
   181						&offset, sizeof(*dire));
   182				if (err < 0)
   183					goto read_failure;
   184	
   185				size = le16_to_cpu(dire->size) + 1;
   186	
   187				/* size should never be larger than SQUASHFS_NAME_LEN */
   188				if (size > SQUASHFS_NAME_LEN)
   189					goto data_error;
   190	
   191				err = squashfs_read_metadata(dir->i_sb, dire->name,
   192						&block, &offset, size);
   193				if (err < 0)
   194					goto read_failure;
   195	
   196				length += sizeof(*dire) + size;
   197	
   198				if (name[0] < dire->name[0])
   199					goto exit_lookup;
   200	
   201				if (len == size && !strncmp(name, dire->name, len)) {
   202					unsigned int blk, off, ino_num;
   203					long long ino;
   204					blk = le32_to_cpu(dirh.start_block);
   205					off = le16_to_cpu(dire->offset);
   206					ino_num = le32_to_cpu(dirh.inode_number) +
   207						(short) le16_to_cpu(dire->inode_number);
   208					ino = squashfs_mkinode(blk, off);
   209	
   210					TRACE("calling squashfs_iget for directory "
   211						"entry %s, inode  %x:%x, %d\n", name,
   212						blk, off, ino_num);
   213	
   214					inode = squashfs_iget(dir->i_sb, ino, ino_num);
   215					goto exit_lookup;
   216				}
   217			}
   218		}
   219	
   220	exit_lookup:
   221		kfree(dire);
   222		return d_splice_alias(inode, dentry);
   223	
   224	data_error:
   225		err = -EIO;
   226	
   227	read_failure:
   228		ERROR("Unable to read directory block [%llx:%x]\n",
   229			squashfs_i(dir)->start, squashfs_i(dir)->offset);
   230	failed:
   231		kfree(dire);
   232		return ERR_PTR(err);
   233	}
   234	

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