Lib/shutil.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Lib/shutil.py b/Lib/shutil.py
index 22bd86d..0e30da2 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -130,8 +130,10 @@ def _fastcopy_sendfile(fsrc, fdst):
     # should not make any difference, also in case the file content
     # changes while being copied.
     try:
+        filesize = os.fstat(infd).st_size
         blocksize = max(os.fstat(infd).st_size, 2 ** 23)  # min 8MiB
     except OSError:
+        filesize = float('inf')
         blocksize = 2 ** 27  # 128MiB
     # On 32-bit architectures truncate to 1GiB to avoid OverflowError,
     # see bpo-38319.
@@ -139,7 +141,7 @@ def _fastcopy_sendfile(fsrc, fdst):
         blocksize = min(blocksize, 2 ** 30)
 
     offset = 0
-    while True:
+    while offset < filesize:
         try:
             sent = os.sendfile(outfd, infd, offset, blocksize)
         except OSError as err: