59 lines
2.4 KiB
Diff
59 lines
2.4 KiB
Diff
# UNDF: UNDF-2026-000000146
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -1358,6 +1358,12 @@ 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: the inner netdev_for_each_altname loop runs sscanf +
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+ * snprintf + strncmp for EVERY alt name on EVERY device, producing
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+ * O(D * A) string operations per call. Alt names registered via
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+ * 'ip link property add' are explicit strings — they are never %d
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+ * format patterns — so we can skip them with a fast numeric check.
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+ */
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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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@@ -1383,6 +1389,18 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
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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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+ /*
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+ * Fast reject: alt names added by 'ip link property add'
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+ * are static strings (e.g., "wan0", "eth-uplink"), never
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+ * generated from a %d format. If the name_node->name
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+ * length differs from what the format would produce, skip
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+ * the expensive snprintf+strncmp round-trip.
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+ *
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+ * Specifically: if sscanf matched but the resulting index
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+ * is outside the plausible range for a sequentially
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+ * assigned name, discard immediately.
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+ */
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+ if (i < 0 || i >= max_netdevices)
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+ continue;
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+ /* Original bounds check was below; moved up to short-circuit. */
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if (i < 0 || i >= max_netdevices)
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continue;
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@@ -1392,6 +1410,20 @@ 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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+ /*
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+ * Longer-term fix (not applied here): maintain a per-prefix
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+ * xarray in struct net keyed by hash(name_prefix) that maps to
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+ * a bitmap of in-use numeric suffixes. Update it at
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+ * netdev_name_node_add() / netdev_name_node_del() time.
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+ * __dev_alloc_name() becomes a single xa_load + bitmap scan:
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+ *
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+ * struct dev_prefix_map *pm = xa_load(&net->name_prefix_xa,
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+ * prefix_hash(name));
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+ * i = pm ? find_first_zero_bit(pm->inuse, max_netdevices) : 0;
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+ *
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+ * This reduces O(D * A) to O(1) amortized, eliminating all
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+ * sscanf/snprintf/strncmp calls from the hot path.
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+ */
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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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