https://github.com/python/cpython/commit/63f196090f90cbfe5f698824655f74dea5cb2b29
commit: 63f196090f90cbfe5f698824655f74dea5cb2b29
branch: main
author: Brian Schubert <[email protected]>
committer: vstinner <[email protected]>
date: 2024-09-20T12:08:59+02:00
summary:
gh-124248: Fix crash in struct when processing 0p fields (#124251)
files:
A Misc/NEWS.d/next/Library/2024-09-19-11-47-39.gh-issue-124248.g7rufd.rst
M Lib/test/test_struct.py
M Misc/ACKS
M Modules/_struct.c
diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
index 5508cc3eec85c8..bdbf8800cfd8f6 100644
--- a/Lib/test/test_struct.py
+++ b/Lib/test/test_struct.py
@@ -96,6 +96,13 @@ def test_new_features(self):
('10s', b'helloworld', b'helloworld', b'helloworld', 0),
('11s', b'helloworld', b'helloworld\0', b'helloworld\0', 1),
('20s', b'helloworld', b'helloworld'+10*b'\0',
b'helloworld'+10*b'\0', 1),
+ ('0p', b'helloworld', b'', b'', 1),
+ ('1p', b'helloworld', b'\x00', b'\x00', 1),
+ ('2p', b'helloworld', b'\x01h', b'\x01h', 1),
+ ('10p', b'helloworld', b'\x09helloworl', b'\x09helloworl', 1),
+ ('11p', b'helloworld', b'\x0Ahelloworld', b'\x0Ahelloworld', 0),
+ ('12p', b'helloworld', b'\x0Ahelloworld\0', b'\x0Ahelloworld\0',
1),
+ ('20p', b'helloworld', b'\x0Ahelloworld'+9*b'\0',
b'\x0Ahelloworld'+9*b'\0', 1),
('b', 7, b'\7', b'\7', 0),
('b', -7, b'\371', b'\371', 0),
('B', 7, b'\7', b'\7', 0),
@@ -339,6 +346,7 @@ def assertStructError(func, *args, **kwargs):
def test_p_code(self):
# Test p ("Pascal string") code.
for code, input, expected, expectedback in [
+ ('0p', b'abc', b'', b''),
('p', b'abc', b'\x00', b''),
('1p', b'abc', b'\x00', b''),
('2p', b'abc', b'\x01a', b'a'),
@@ -580,6 +588,7 @@ def test__sizeof__(self):
self.check_sizeof('187s', 1)
self.check_sizeof('20p', 1)
self.check_sizeof('0s', 1)
+ self.check_sizeof('0p', 1)
self.check_sizeof('0c', 0)
def test_boundary_error_message(self):
diff --git a/Misc/ACKS b/Misc/ACKS
index b031eb7c11f73f..2db17adcc2ee66 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1653,6 +1653,7 @@ Scott Schram
Robin Schreiber
Chad J. Schroeder
Simon-Martin Schroeder
+Brian Schubert
Christian Schubert
Sam Schulenburg
Andreas Schwab
diff --git
a/Misc/NEWS.d/next/Library/2024-09-19-11-47-39.gh-issue-124248.g7rufd.rst
b/Misc/NEWS.d/next/Library/2024-09-19-11-47-39.gh-issue-124248.g7rufd.rst
new file mode 100644
index 00000000000000..1bd333f485a2ab
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-09-19-11-47-39.gh-issue-124248.g7rufd.rst
@@ -0,0 +1,2 @@
+Fixed potential crash when using :mod:`struct` to process zero-width
+'Pascal string' fields (``0p``).
diff --git a/Modules/_struct.c b/Modules/_struct.c
index f744193469e2dc..2ae5060ba34163 100644
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -1669,9 +1669,16 @@ s_unpack_internal(PyStructObject *soself, const char
*startfrom,
if (e->format == 's') {
v = PyBytes_FromStringAndSize(res, code->size);
} else if (e->format == 'p') {
- Py_ssize_t n = *(unsigned char*)res;
- if (n >= code->size)
- n = code->size - 1;
+ Py_ssize_t n;
+ if (code->size == 0) {
+ n = 0;
+ }
+ else {
+ n = *(unsigned char*)res;
+ if (n >= code->size) {
+ n = code->size - 1;
+ }
+ }
v = PyBytes_FromStringAndSize(res + 1, n);
} else {
v = e->unpack(state, res, e);
@@ -1982,8 +1989,12 @@ s_pack_internal(PyStructObject *soself, PyObject *const
*args, int offset,
n = PyByteArray_GET_SIZE(v);
p = PyByteArray_AS_STRING(v);
}
- if (n > (code->size - 1))
+ if (code->size == 0) {
+ n = 0;
+ }
+ else if (n > (code->size - 1)) {
n = code->size - 1;
+ }
if (n > 0)
memcpy(res + 1, p, n);
if (n > 255)
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