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Guard surrounding_text against out-of-bounds cursor/anchor offsets #133

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Guard surrounding_text against out-of-bounds cursor/anchor offsets #133

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8 changes: 8 additions & 0 deletions connection/waylandinputmethodconnection.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -596,6 +596,14 @@ void InputMethodContext::zwp_input_method_context_v1_surrounding_text(const QStr

const QByteArray &utf8_text(text.toUtf8());

// cursor and anchor are byte offsets supplied by the compositor and cannot be
// trusted: a bogus value larger than the text (seen in the wild as e.g. 6881396)
// makes the QString::fromUtf8 calls below read past the end of utf8_text and
// crash. Clamp them to the actual length before using them as offsets/lengths.
const uint32_t utf8_len = static_cast<uint32_t>(utf8_text.size());
cursor = qMin(cursor, utf8_len);
anchor = qMin(anchor, utf8_len);

m_stateInfo[SurroundingTextAttribute] = text;
m_stateInfo[CursorPositionAttribute] = QString::fromUtf8(utf8_text.constData(), cursor).size();
m_stateInfo[AnchorPositionAttribute] = QString::fromUtf8(utf8_text.constData(), anchor).size();
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