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bpo-36819: Fix crashes in built-in encoders with weird error handlers (GH-28593)

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If the error handler returns position less or equal than the starting
position of non-encodable characters, most of built-in encoders didn't
properly re-size the output buffer. This led to out-of-bounds writes,
and segfaults.
This commit is contained in:
Serhiy Storchaka 2022-05-02 12:37:48 +03:00 • committed by GitHub
parent 614420df97
commit 18b07d773e
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4 changed files with 222 additions and 32 deletions
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15
Objects/stringlib/codecs.h
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@ -387,8 +387,19 @@ STRINGLIB(utf8_encoder)(_PyBytesWriter *writer,
if (!rep)
goto error;
/* subtract preallocated bytes */
writer->min_size -= max_char_size * (newpos - startpos);
if (newpos < startpos) {
writer->overallocate = 1;
p = _PyBytesWriter_Prepare(writer, p,
max_char_size * (startpos - newpos));
if (p == NULL)
goto error;
}
else {
/* subtract preallocated bytes */
writer->min_size -= max_char_size * (newpos - startpos);
/* Only overallocate the buffer if it's not the last write */
writer->overallocate = (newpos < size);
}
if (PyBytes_Check(rep)) {
p = _PyBytesWriter_WriteBytes(writer, p,