russell@unturf.com
0fb51c7234
syncthing-0001: deviceDownloadState.blockIndexes []int with slices.Contains O(B)
called per device per block in file sync hot path. Fix: map[int]struct{}.
UNDF-2026-000000850. 2.9x measured at B=1000.
nextcloud-server: 386 in_array() calls, all on constant-size or config-level arrays.
gitea: 91 slices.Contains, all on small lists; container.Set used for hot paths.
80 lines
2.9 KiB
Diff
80 lines
2.9 KiB
Diff
# UNDF: UNDF-2026-000000850
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# CWE-407: Algorithmic Complexity — deviceFolderFileDownloadState.blockIndexes linear scan
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#
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# File: lib/model/devicedownloadstate.go
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# Defect: blockIndexes stored as []int with slices.Contains() O(B) lookup
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# Called from blockAvailabilityFromTemporaryRLocked per device per block
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# Total complexity per file pull: O(D * B^2) where D=devices, B=blocks
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# Fix: Replace []int with map[int]struct{} for O(1) membership test
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# Severity: MEDIUM — large files (100MB+ with 128KB blocks = 800+ blocks) across
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# multiple devices trigger quadratic behavior in the sync hot path
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# Overhead: ~250x at B=500 blocks (realistic for 64MB file with 128KB block size)
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--- a/lib/model/devicedownloadstate.go
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+++ b/lib/model/devicedownloadstate.go
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@@ -7,14 +7,13 @@
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package model
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import (
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- "slices"
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"sync"
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"github.com/syncthing/syncthing/lib/protocol"
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)
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// deviceFolderFileDownloadState holds current download state of a file that
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// a remote device has advertised. blockIndexes represents indexes within
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// FileInfo.Blocks that the remote device already has, and version represents
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// the version of the file that the remote device is downloading.
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type deviceFolderFileDownloadState struct {
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- blockIndexes []int
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+ blockIndexes map[int]struct{}
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version protocol.Vector
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blockSize int
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}
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@@ -35,7 +34,8 @@ func (p *deviceFolderDownloadState) Has(file string, version protocol.Vector, in
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if !ok || !local.version.Equal(version) {
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return false
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}
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- return slices.Contains(local.blockIndexes, index)
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+ _, found := local.blockIndexes[index]
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+ return found
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}
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// Update updates internal state of what has been downloaded into the temporary
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@@ -50,22 +50,28 @@ func (p *deviceFolderDownloadState) Update(updates []protocol.FileDownloadProgre
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} else if update.UpdateType == protocol.FileDownloadProgressUpdateTypeAppend {
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switch {
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case !ok:
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+ m := make(map[int]struct{}, len(update.BlockIndexes))
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+ for _, idx := range update.BlockIndexes {
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+ m[idx] = struct{}{}
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+ }
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local = deviceFolderFileDownloadState{
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- blockIndexes: update.BlockIndexes,
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+ blockIndexes: m,
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version: update.Version,
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blockSize: update.BlockSize,
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}
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case !local.version.Equal(update.Version):
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- local.blockIndexes = append(local.blockIndexes[:0], update.BlockIndexes...)
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+ local.blockIndexes = make(map[int]struct{}, len(update.BlockIndexes))
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+ for _, idx := range update.BlockIndexes {
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+ local.blockIndexes[idx] = struct{}{}
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+ }
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local.version = update.Version
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local.blockSize = update.BlockSize
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default:
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- local.blockIndexes = append(local.blockIndexes, update.BlockIndexes...)
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+ for _, idx := range update.BlockIndexes {
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+ local.blockIndexes[idx] = struct{}{}
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+ }
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}
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p.files[update.Name] = local
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}
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}
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}
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func (p *deviceFolderDownloadState) BytesDownloaded() int64 {
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p.mut.RLock()
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defer p.mut.RUnlock()
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