Issue #10955: Fix a potential crash when trying to mmap() a file past its

length.  Initial patch by Ross Lagerwall.

This fixes a regression introduced by r88022.

1 files changed, 13 insertions, 0 deletions

diff --git a/Lib/test/test_mmap.py b/Lib/test/test_mmap.py
index 08b0714..8f20d96 100644
--- a/Lib/test/test_mmap.py
+++ b/Lib/test/test_mmap.py
@@ -334,6 +334,19 @@ class MmapTests(unittest.TestCase):
             with mmap.mmap(f.fileno(), 0, offset=65536, access=mmap.ACCESS_READ) as mf:
                 self.assertRaises(IndexError, mf.__getitem__, 80000)
 
+    def test_length_0_large_offset(self):
+        # Issue #10959: test mapping of a file by passing 0 for
+        # map length with a large offset doesn't cause a segfault.
+        if not hasattr(os, "stat"):
+            self.skipTest("needs os.stat")
+
+        with open(TESTFN, "wb") as f:
+            f.write(115699 * b'm') # Arbitrary character
+
+        with open(TESTFN, "w+b") as f:
+            self.assertRaises(ValueError, mmap.mmap, f.fileno(), 0,
+                              offset=2147418112)
+
     def test_move(self):
         # make move works everywhere (64-bit format problem earlier)
         f = open(TESTFN, 'wb+')