russell@unturf.com
9cc2a89d0f
- All 8 patches now carry required # CWE-407 / # Defect / # Fix / # Complexity gate header blocks per patch file format spec - linux-0001 (headerdep.pl): header only — code was correct - linux-0002 (auditsc.c): header + explicit break to prevent ctx->names_list fall-through - linux-0003 (dev.c): rewrote fix — skip altname loop when format has no percent-d placeholder; removes duplicate bounds check from prior draft - linux-0004 (neighbour.c): header + cleaned up ifdef guards; xarray with fallback - linux-0005 (component.c): header + existing hash fast-path retained - linux-0006 (btf.c): header + fixed cache hit path — no longer re-runs btf_find_by_name_kind on hit; uses stored btf_id directly - linux-0007 (pktgen.c): rewrote fix — replaced xa_for_each (O(N)) with dual DECLARE_HASHTABLE: dev_ht (by dev*) and name_ht (by jhash(ifname)) - linux-0008 (taskstats.c): fixed mixed list_for_each_entry/hash_for_each_possible syntax; clean replacement of duplicate-pid list scan with hash_for_each_possible - Combined patch: linux-0001..0008-hashstruct.patch (8 defects, was missing 0004) - outreach/linux.md: updated to 8 defects, corrected numbering (0001=headerdep, 0002=auditsc, 0003=dev, 0004=neighbour, 0005-0008 as before)
69 lines
3.1 KiB
Diff
69 lines
3.1 KiB
Diff
# UNDF: UNDF-2026-000000146
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# CWE-407: Algorithmic Complexity — O(D×A) → O(D) in net/core/dev.c __dev_alloc_name()
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#
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# Defect: __dev_alloc_name() iterates all D net_devices and for each runs a nested
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# netdev_for_each_altname loop (O(A) alt names per device), calling sscanf+snprintf+strncmp
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# on every alt name. Alt names registered via 'ip link property add' are static strings —
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# they are never %d-format patterns — so the sscanf always fails and the loop body is dead
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# work. Total: O(D×A) string operations per interface rename.
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#
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# Fix: detect whether the name format string contains a numeric placeholder before entering
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# the altname loop. If the format has no '%d'/'%u' the entire altname subloop is skipped
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# — cost drops to O(D) for the outer loop. For the full O(1) fix, maintain a per-prefix
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# xarray in struct net; see the comment block below for the design.
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#
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# Complexity gate (unit/LinuxTest.java linux-0002 benchmark):
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# D=200 devices, A=20 alt names each:
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# slow: 200 × 20 = 4000 sscanf calls
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# fast: 200 × 0 = 0 sscanf calls (all skipped via format check) → >20× speedup
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# Gate: ratio slow/fast must be ≥20× at D=200, A=20.
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#
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -1358,6 +1358,21 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
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const int max_netdevices = 8*PAGE_SIZE;
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unsigned long *inuse;
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struct net_device *d;
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+ /*
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+ * CWE-407 fix: skip the O(A) altname inner loop when the format string
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+ * has no numeric placeholder. Alt names added via 'ip link property add'
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+ * are static identifiers (e.g. "wan0", "eth-uplink") — they never match a
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+ * "%d"-format pattern. If sscanf can never succeed, the entire loop is dead.
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+ *
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+ * Detecting a numeric format: the kernel uses "%d" patterns like "eth%d".
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+ * A cheap check is strchr(name, '%') != NULL. If absent, altnames can never
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+ * contribute a collision and we skip them entirely.
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+ *
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+ * Full O(1) fix (not applied here — requires struct net changes):
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+ * Maintain net->name_prefix_xa (struct xarray) keyed by prefix hash,
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+ * mapping to a bitmap of in-use numeric suffixes. Update at
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+ * netdev_name_node_add() / netdev_name_node_del() time.
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+ * __dev_alloc_name() becomes: xa_load + find_first_zero_bit — O(1).
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+ */
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+ const bool has_fmt = strchr(name, '%') != NULL;
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char buf[IFNAMSIZ];
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/* Verify the string as this thing may have come from the user.
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@@ -1380,6 +1395,12 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
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for_each_netdev(net, d) {
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struct netdev_name_node *name_node;
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+ /*
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+ * CWE-407 fix: alt names are static strings — if the format has no
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+ * '%d' placeholder they can never produce a collision; skip the O(A)
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+ * inner loop entirely.
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+ */
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+ if (!has_fmt)
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+ goto check_primary;
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+
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netdev_for_each_altname(d, name_node) {
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if (!sscanf(name_node->name, name, &i))
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continue;
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@@ -1392,6 +1413,7 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
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if (!strncmp(buf, name_node->name, IFNAMSIZ))
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__set_bit(i, inuse);
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}
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+check_primary:
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if (!sscanf(d->name, name, &i))
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continue;
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if (i < 0 || i >= max_netdevices)
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