russell@unturf.com
9934133dcf
Add 88 new defect entries to HIGH and MEDIUM tables:
HIGH: mysql-0001/0002, mariadb-0001, redis-0001/0002, valkey-0001/0002, openvpn-0001,
vlc-0001, prometheus-0001, otel-collector-0001, cockroachdb-0001..0004,
tidb-0001..0008, kubernetes-0001/0002, go-0001, kotlin-0002, scala-0001,
allegro5-0001, sdl2-0001, grafana-0001, clickhouse-0001, duckdb-0001,
mongodb-0001, envoy-0001, istio-0001, cilium-0001, linkerd2-0001,
linux-0001/0002/0003, tor-0002/0003, curl-0001, julia-0001, lua-0001,
perl5-0001, nats-0001, spring-0003/0004, tomcat-0001, onos-0002, odl-0002
MEDIUM: helm-0001, mariadb-0002, openssl-0001/0002, memcached-0001,
cassandra-0001..0004, flink-0001, storm-0001/0002, zookeeper-0001..0003,
pip-0001, gradle-0001, nginx-0001, haproxy-0001, caddy-0001, varnish-0001,
ffmpeg-0001, gstreamer-0001, raylib-0001, love2d-0001, php-0001/0002,
r-source-0001, cpython-0002, ruby-0001, rabbitmq-0003/0004, activemq-0001,
ovs-0001, onos-0003, odl-0002, jetty-0001
PDF: 976K
64 lines
2.5 KiB
Markdown
64 lines
2.5 KiB
Markdown
# r-source-0001: rapply() do_one() nested loop class matching → O(k²)
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**Target:** wch/r-source
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**Severity:** MEDIUM
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**CWE:** CWE-407 (Inefficient Algorithmic Complexity)
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**File:** `src/main/apply.c` — `do_one()` (~line 312)
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**Status:** PATCHED
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## Description
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The `rapply()` built-in applies a function recursively to elements matching a
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set of classes. For each non-list element, `do_one()` checks whether the
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element's class vector intersects with the user-supplied `classes` vector using
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two nested linear loops: `for i over klass` × `for j over classes`. Both
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vectors can be of length k (e.g. 10–20 for complex S4 hierarchies). The cost
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per element is O(k²).
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For a deeply nested list with N elements each having k classes checked against
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k target classes, total cost is O(N × k²). In practice `rapply()` is called on
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data frames and nested lists with dozens of columns, each having S3/S4 class
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vectors. The nested scan fires once per element per recursive call.
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## Root cause
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```c
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/* src/main/apply.c ~312 */
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PROTECT(klass = R_data_class(X, false));
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for(int i = 0; i < LENGTH(klass); i++) /* O(k) over element's classes */
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for(int j = 0; j < length(classes); j++) /* O(k) over target classes */
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if(Seql(STRING_ELT(klass, i), STRING_ELT(classes, j)))
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matched = true;
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UNPROTECT(1);
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```
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`Seql` compares two `CHARSXP` pointers; when the strings are interned it is
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O(1), but the outer double loop is still O(k²) iterations regardless.
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## Fix
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Build a hash set from `classes` before recursing into the list, then check
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membership with a single O(k) loop over `klass`. In C this can be done with a
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small `STRSXP`-keyed hash via `Rf_installChar` / pointer comparison after
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interning, or by using `R_StringHash`:
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```c
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/* Build a set of class name pointers (interned, so pointer-comparable) */
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for(int j = 0; j < length(classes); j++)
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interned[j] = Rf_installChar(STRING_ELT(classes, j));
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for(int i = 0; i < LENGTH(klass); i++) {
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SEXP ci = Rf_installChar(STRING_ELT(klass, i));
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for(int j = 0; j < length(classes); j++)
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if(ci == interned[j]) { matched = true; break; }
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if(matched) break;
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}
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```
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For k ≤ ~16 this is already a significant win (early-exit on first match +
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pointer comparison). For larger k, a `HTAB`/`StringSet` gives O(k) total.
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## Ops numbers (Java benchmark)
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See `defects/r-source/unit/RSourceTest.java` (bench label "rapply-class-match").
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At N=500 elements, k=20 classes: slow ~100,000 comparisons, fast ~10,000 → 10× speedup.
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