Issue #5677: Explicitly forbid write operations on read-only file objects,
and read operations on write-only file objects. On Windows, the system C
library would return a bogus result; on Solaris, it was possible to crash
the interpreter. Patch by Stefan Krah.
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 3220702..6456368 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -167,6 +167,13 @@
f->f_encoding = Py_None;
Py_INCREF(Py_None);
f->f_errors = Py_None;
+ f->readable = f->writable = 0;
+ if (strchr(mode, 'r') != NULL || f->f_univ_newline)
+ f->readable = 1;
+ if (strchr(mode, 'w') != NULL || strchr(mode, 'a') != NULL)
+ f->writable = 1;
+ if (strchr(mode, '+') != NULL)
+ f->readable = f->writable = 1;
if (f->f_mode == NULL)
return NULL;
@@ -568,6 +575,13 @@
return NULL;
}
+static PyObject *
+err_mode(char *action)
+{
+ PyErr_Format(PyExc_IOError, "File not open for %s", action);
+ return NULL;
+}
+
/* Refuse regular file I/O if there's data in the iteration-buffer.
* Mixing them would cause data to arrive out of order, as the read*
* methods don't use the iteration buffer. */
@@ -782,6 +796,8 @@
if (f->f_fp == NULL)
return err_closed();
+ if (!f->writable)
+ return err_mode("writing");
if (!PyArg_UnpackTuple(args, "truncate", 0, 1, &newsizeobj))
return NULL;
@@ -1030,6 +1046,8 @@
if (f->f_fp == NULL)
return err_closed();
+ if (!f->readable)
+ return err_mode("reading");
/* refuse to mix with f.next() */
if (f->f_buf != NULL &&
(f->f_bufend - f->f_bufptr) > 0 &&
@@ -1099,6 +1117,8 @@
if (f->f_fp == NULL)
return err_closed();
+ if (!f->readable)
+ return err_mode("reading");
/* refuse to mix with f.next() */
if (f->f_buf != NULL &&
(f->f_bufend - f->f_bufptr) > 0 &&
@@ -1470,6 +1490,8 @@
PyFileObject *fo = (PyFileObject *)f;
if (fo->f_fp == NULL)
return err_closed();
+ if (!fo->readable)
+ return err_mode("reading");
/* refuse to mix with f.next() */
if (fo->f_buf != NULL &&
(fo->f_bufend - fo->f_bufptr) > 0 &&
@@ -1558,6 +1580,8 @@
if (f->f_fp == NULL)
return err_closed();
+ if (!f->readable)
+ return err_mode("reading");
/* refuse to mix with f.next() */
if (f->f_buf != NULL &&
(f->f_bufend - f->f_bufptr) > 0 &&
@@ -1591,6 +1615,8 @@
if (f->f_fp == NULL)
return err_closed();
+ if (!f->readable)
+ return err_mode("reading");
/* refuse to mix with f.next() */
if (f->f_buf != NULL &&
(f->f_bufend - f->f_bufptr) > 0 &&
@@ -1709,6 +1735,8 @@
Py_ssize_t n, n2;
if (f->f_fp == NULL)
return err_closed();
+ if (!f->writable)
+ return err_mode("writing");
if (f->f_binary) {
if (!PyArg_ParseTuple(args, "s*", &pbuf))
return NULL;
@@ -1746,6 +1774,8 @@
assert(seq != NULL);
if (f->f_fp == NULL)
return err_closed();
+ if (!f->writable)
+ return err_mode("writing");
result = NULL;
list = NULL;
@@ -2186,6 +2216,8 @@
if (f->f_fp == NULL)
return err_closed();
+ if (!f->readable)
+ return err_mode("reading");
l = readahead_get_line_skip(f, 0, READAHEAD_BUFSIZE);
if (l == NULL || PyString_GET_SIZE(l) == 0) {