From 6e3b7982dbcf8087374694253e0e248fbc6c6e3e Mon Sep 17 00:00:00 2001 From: m-holger Date: Wed, 17 Jan 2024 10:39:06 +0000 Subject: Fix incorrect handling of invalid negative object ids Fix two errors introduced in #1110 and #1112. Since #1110, encountering the invalid indirect reference #1110 -2147483648 n R produces an integer underflow which, if undetected, immediately trigger a logic error. Since #1112, object -1 0 R may be incorrectly identified as an earlier generation of itself and deleted, invalidating a live iterator. --- libqpdf/QPDF.cc | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'libqpdf') diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc index 89d4a0a8..8cff3dfd 100644 --- a/libqpdf/QPDF.cc +++ b/libqpdf/QPDF.cc @@ -709,10 +709,11 @@ QPDF::read_xref(qpdf_offset_t xref_offset) // Make sure we keep only the highest generation for any object. QPDFObjGen last_og{-1, 0}; - for (auto const& og: m->xref_table) { - if (og.first.getObj() == last_og.getObj()) + for (auto const& item: m->xref_table) { + auto id = item.first.getObj(); + if (id == last_og.getObj() && id > 0) removeObject(last_og); - last_og = og.first; + last_og = item.first; } } @@ -2405,7 +2406,7 @@ QPDF::getCompressibleObjGens() while (!queue.empty()) { auto obj = queue.back(); queue.pop_back(); - if (obj.isIndirect()) { + if (obj.getObjectID() > 0) { QPDFObjGen og = obj.getObjGen(); const size_t id = toS(og.getObj() - 1); if (id >= max_obj) -- cgit v1.2.3-54-g00ecf