40 lines
1.5 KiB
Diff
40 lines
1.5 KiB
Diff
# UNDF: UNDF-2026-000000348
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From HEAD Mon Sep 17 00:00:00 2001
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Subject: [PATCH] slabs: replace linear scan in slabs_clsid with binary search
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CWE-407: slabs_clsid() walks the slabclass[] array linearly to find the
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smallest class that fits a requested size. slabclass[] is sorted ascending
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by size (guaranteed by slabs_init), so binary search applies.
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With up to 63 slab classes (MAX_NUMBER_OF_SLAB_CLASSES-1) linear search
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performs up to 63 comparisons; binary search performs at most 6 (⌈log₂63⌉).
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slabs_clsid is called on every item allocation (do_item_alloc, do_item_alloc_chunk,
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item_store_check) making it a hot path at high write throughput.
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--- a/slabs.c
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+++ b/slabs.c
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@@ -77,12 +77,19 @@ unsigned int slabs_size(const int clsid) {
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unsigned int slabs_clsid(const size_t size) {
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- int res = POWER_SMALLEST;
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-
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if (size == 0 || size > settings.item_size_max)
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return 0;
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- while (size > slabclass[res].size)
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- if (res++ == power_largest) /* won't fit in the biggest slab */
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- return power_largest;
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- return res;
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+
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+ /* CWE-407 fix: binary search over sorted slabclass[POWER_SMALLEST..power_largest].
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+ * slabs_init guarantees strictly increasing .size values. */
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+ int lo = POWER_SMALLEST, hi = power_largest;
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+ while (lo < hi) {
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+ int mid = lo + (hi - lo) / 2;
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+ if (slabclass[mid].size < size)
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+ lo = mid + 1;
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+ else
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+ hi = mid;
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+ }
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+ /* lo == hi == smallest class whose size >= requested size */
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+ return lo;
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}
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