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.
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 @@
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+')
diff --git a/Misc/NEWS b/Misc/NEWS
index 03912b3..44d39cf 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -16,6 +16,9 @@
Library
-------
+- Issue #10955: Fix a potential crash when trying to mmap() a file past its
+ length. Initial patch by Ross Lagerwall.
+
- Issue #10898: Allow compiling the posix module when the C library defines
a symbol named FSTAT.
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index f3b2f50..a9049ed 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -1116,6 +1116,11 @@
# endif
if (fd != -1 && fstat(fd, &st) == 0 && S_ISREG(st.st_mode)) {
if (map_size == 0) {
+ if (offset >= st.st_size) {
+ PyErr_SetString(PyExc_ValueError,
+ "mmap offset is greater than file size");
+ return NULL;
+ }
map_size = st.st_size - offset;
} else if ((size_t)offset + (size_t)map_size > st.st_size) {
PyErr_SetString(PyExc_ValueError,
@@ -1300,6 +1305,12 @@
else
m_obj->size = low;
#endif
+ if (offset >= m_obj->size) {
+ PyErr_SetString(PyExc_ValueError,
+ "mmap offset is greater than file size");
+ Py_DECREF(m_obj);
+ return NULL;
+ }
m_obj->size -= offset;
} else {
m_obj->size = map_size;