f2fs: add a condition to detect overflow in f2fs_ioc_gc_range()

end = range.start + range.len;

If the range.start/range.len is a very large value, then end can overflow
in this operation. It results into a crash in get_valid_blocks() when
accessing the invalid range.start segno.

This issue is reported in ioctl fuzz testing.
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -2264,9 +2264,9 @@ static int f2fs_ioc_gc_range(struct file *filp, unsigned long arg)
 		return -EROFS;
 
 	end = range.start + range.len;
-	if (range.start < MAIN_BLKADDR(sbi) || end >= MAX_BLKADDR(sbi)) {
+	if (end < range.start || range.start < MAIN_BLKADDR(sbi) ||
+					end >= MAX_BLKADDR(sbi))
 		return -EINVAL;
-	}
 
 	ret = mnt_want_write_file(filp);
 	if (ret)