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Issue #16350, part 2: Set unused_data (and unconsumed_tail) correctly in decompressobj().flush().

Browse source 
Additionally, fix a bug where a MemoryError in allocating a bytes object could
leave the decompressor object in an invalid state (with its unconsumed_tail
member being NULL).

Patch by Serhiy Storchaka.
This commit is contained in:
Nadeem Vawda 2012-11-11 02:21:22 +01:00
commit dd1253abdd
3 changed files with 80 additions and 56 deletions
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98
Modules/zlibmodule.c
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@ -561,6 +561,49 @@ PyZlib_objcompress(compobject *self, PyObject *args)
return RetVal;
}
/* Helper for objdecompress() and unflush(). Saves any unconsumed input data in
self->unused_data or self->unconsumed_tail, as appropriate. */
static int
save_unconsumed_input(compobject *self, int err)
{
if (err == Z_STREAM_END) {
/* The end of the compressed data has been reached. Store the leftover
input data in self->unused_data. */
if (self->zst.avail_in > 0) {
Py_ssize_t old_size = PyBytes_GET_SIZE(self->unused_data);
Py_ssize_t new_size;
PyObject *new_data;
if (self->zst.avail_in > PY_SSIZE_T_MAX - old_size) {
PyErr_NoMemory();
return -1;
}
new_size = old_size + self->zst.avail_in;
new_data = PyBytes_FromStringAndSize(NULL, new_size);
if (new_data == NULL)
return -1;
Py_MEMCPY(PyBytes_AS_STRING(new_data),
PyBytes_AS_STRING(self->unused_data), old_size);
Py_MEMCPY(PyBytes_AS_STRING(new_data) + old_size,
self->zst.next_in, self->zst.avail_in);
Py_DECREF(self->unused_data);
self->unused_data = new_data;
self->zst.avail_in = 0;
}
}
if (self->zst.avail_in > 0 || PyBytes_GET_SIZE(self->unconsumed_tail)) {
/* This code handles two distinct cases:
1. Output limit was reached. Save leftover input in unconsumed_tail.
2. All input data was consumed. Clear unconsumed_tail. */
PyObject *new_data = PyBytes_FromStringAndSize(
(char *)self->zst.next_in, self->zst.avail_in);
if (new_data == NULL)
return -1;
Py_DECREF(self->unconsumed_tail);
self->unconsumed_tail = new_data;
}
return 0;
}
PyDoc_STRVAR(decomp_decompress__doc__,
"decompress(data, max_length) -- Return a string containing the decompressed\n"
"version of the data.\n"
@ -668,61 +711,21 @@ PyZlib_objdecompress(compobject *self, PyObject *args)
Py_END_ALLOW_THREADS
}
if(max_length) {
/* Not all of the compressed data could be accommodated in a buffer of
the specified size. Return the unconsumed tail in an attribute. */
Py_DECREF(self->unconsumed_tail);
self->unconsumed_tail = PyBytes_FromStringAndSize((char *)self->zst.next_in,
self->zst.avail_in);
}
else if (PyBytes_GET_SIZE(self->unconsumed_tail) > 0) {
/* All of the compressed data was consumed. Clear unconsumed_tail. */
Py_DECREF(self->unconsumed_tail);
self->unconsumed_tail = PyBytes_FromStringAndSize("", 0);
}
if (self->unconsumed_tail == NULL) {
if (save_unconsumed_input(self, err) < 0) {
Py_DECREF(RetVal);
RetVal = NULL;
goto error;
}
/* The end of the compressed data has been reached, so set the
unused_data attribute to a string containing the remainder of the
data in the string. Note that this is also a logical place to call
inflateEnd, but the old behaviour of only calling it on flush() is
preserved.
*/
if (err == Z_STREAM_END) {
if (self->zst.avail_in > 0) {
/* Append the leftover data to the existing value of unused_data. */
Py_ssize_t old_size = PyBytes_GET_SIZE(self->unused_data);
Py_ssize_t new_size = old_size + self->zst.avail_in;
PyObject *new_data;
if (new_size <= old_size) { /* Check for overflow. */
PyErr_NoMemory();
Py_DECREF(RetVal);
RetVal = NULL;
goto error;
}
new_data = PyBytes_FromStringAndSize(NULL, new_size);
if (new_data == NULL) {
Py_DECREF(RetVal);
RetVal = NULL;
goto error;
}
Py_MEMCPY(PyBytes_AS_STRING(new_data),
PyBytes_AS_STRING(self->unused_data), old_size);
Py_MEMCPY(PyBytes_AS_STRING(new_data) + old_size,
self->zst.next_in, self->zst.avail_in);
Py_DECREF(self->unused_data);
self->unused_data = new_data;
}
/* This is the logical place to call inflateEnd, but the old behaviour
of only calling it on flush() is preserved. */
self->eof = 1;
} else if (err != Z_OK && err != Z_BUF_ERROR) {
/* We will only get Z_BUF_ERROR if the output buffer was full
but there wasn't more output when we tried again, so it is
not an error condition.
*/
} else if (err != Z_OK && err != Z_BUF_ERROR) {
zlib_error(self->zst, err, "while decompressing data");
Py_DECREF(RetVal);
RetVal = NULL;
@ -996,6 +999,12 @@ PyZlib_unflush(compobject *self, PyObject *args)
Py_END_ALLOW_THREADS
}
if (save_unconsumed_input(self, err) < 0) {
Py_DECREF(retval);
retval = NULL;
goto error;
}
/* If at end of stream, clean up any memory allocated by zlib. */
if (err == Z_STREAM_END) {
self->eof = 1;
@ -1008,6 +1017,7 @@ PyZlib_unflush(compobject *self, PyObject *args)
goto error;
}
}
if (_PyBytes_Resize(&retval, self->zst.total_out - start_total_out) < 0) {
Py_DECREF(retval);
retval = NULL;