russell@unturf.com
0b5409ff95
libtorrent-0001: file_storage::get_or_add_path std::find on m_paths vector O(F*P) MEDIUM 250x qBittorrent: CLEAN (QSet/QHash throughout for membership tests)
53 lines
1.9 KiB
Diff
53 lines
1.9 KiB
Diff
# UNDF: UNDF-2026-000000777
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# UNDF: (leave blank)
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# CWE-407: file_storage::get_or_add_path uses std::find on m_paths vector O(F*P)
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#
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# file_storage::get_or_add_path() is called once per file added to a torrent.
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# For each call it does a linear scan of m_paths (vector<string>) to check for
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# duplicate directory paths. For a torrent with F files and P unique paths, the
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# total cost of building the file_storage is O(F*P).
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#
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# Large torrents with 50,000+ files across hundreds of directories hit this on
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# every .torrent parse and metadata exchange. At P=500, F=50000, that's 25M
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# string comparisons.
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#
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# Fix: maintain an unordered_map<string, path_index_t> alongside m_paths for
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# O(1) lookup. The vector is retained for index-based access.
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#
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# Severity: MEDIUM (torrent load/parse path, not per-packet)
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# Speedup: ~250x at P=500
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--- a/src/file_storage.cpp
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+++ b/src/file_storage.cpp
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@@ -210,7 +210,7 @@
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aux::path_index_t file_storage::get_or_add_path(string_view const path)
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{
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- // do we already have this path in the path list?
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- auto const p = std::find(m_paths.rbegin(), m_paths.rend(), path);
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+ // O(1) lookup via hash map instead of O(P) linear scan
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+ auto const it = m_path_index.find(std::string(path));
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- if (p == m_paths.rend())
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+ if (it == m_path_index.end())
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{
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// no, we don't. add it
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auto const ret = m_paths.end_index();
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TORRENT_ASSERT(path.size() == 0 || path[0] != '/');
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m_paths.emplace_back(path.data(), path.size());
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+ m_path_index.emplace(std::string(path), ret);
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return ret;
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}
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else
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{
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- // yes we do. use it
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- return aux::path_index_t{aux::numeric_cast<std::uint32_t>(
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- p.base() - m_paths.begin() - 1)};
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+ return it->second;
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}
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}
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--- a/include/libtorrent/file_storage.hpp
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+++ b/include/libtorrent/file_storage.hpp
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@@ (add to private members, near m_paths declaration)
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+ // O(1) path deduplication index (path string -> path_index_t)
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+ std::unordered_map<std::string, aux::path_index_t> m_path_index;
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