From f78b119364b521307237a1484ba5f43f42300898 Mon Sep 17 00:00:00 2001 From: Andrew Nester Date: Tue, 4 Apr 2017 13:46:25 +0300 Subject: bpo-29649: Improve struct.pack_into() boundary error messages (#424) --- Modules/_struct.c | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-) (limited to 'Modules/_struct.c') diff --git a/Modules/_struct.c b/Modules/_struct.c index f66ee18bc4..4bc4186923 100644 --- a/Modules/_struct.c +++ b/Modules/_struct.c @@ -1931,14 +1931,40 @@ s_pack_into(PyObject *self, PyObject **args, Py_ssize_t nargs, PyObject *kwnames } /* Support negative offsets. */ - if (offset < 0) + if (offset < 0) { + /* Check that negative offset is low enough to fit data */ + if (offset + soself->s_size > 0) { + PyErr_Format(StructError, + "no space to pack %zd bytes at offset %zd", + soself->s_size, + offset); + PyBuffer_Release(&buffer); + return NULL; + } + + /* Check that negative offset is not crossing buffer boundary */ + if (offset + buffer.len < 0) { + PyErr_Format(StructError, + "offset %zd out of range for %zd-byte buffer", + offset, + buffer.len); + PyBuffer_Release(&buffer); + return NULL; + } + offset += buffer.len; + } /* Check boundaries */ - if (offset < 0 || (buffer.len - offset) < soself->s_size) { + if ((buffer.len - offset) < soself->s_size) { PyErr_Format(StructError, - "pack_into requires a buffer of at least %zd bytes", - soself->s_size); + "pack_into requires a buffer of at least %zd bytes for " + "packing %zd bytes at offset %zd " + "(actual buffer size is %zd)", + soself->s_size + offset, + soself->s_size, + offset, + buffer.len); PyBuffer_Release(&buffer); return NULL; } -- cgit v1.2.1