x/tools/gopls: SEGV accessing map[string]...

[adonovan]

#!stacks
"runtime.sigpanic" &&
   "runtime.mapaccess2_faststr:+84" &&
   "imports.(*DirInfoCache).Load:+3"

Issue created by stacks.

imports.(*DirInfoCache).Load:

	info, ok := d.dirs[dir]

In mapaccess2_faststr below, it looks like one of k, key, or b is an invalid (nil or corrupt) pointer. We know that b and key are non-nil; and k is derived from b.keys(), which is an offset of b; so the only possibility is data corruption.

	top := tophash(hash)
	for ; b != nil; b = b.overflow(t) {
		for i, kptr := uintptr(0), b.keys(); i < abi.MapBucketCount; i, kptr = i+1, add(kptr, 2*goarch.PtrSize) {
			k := (*stringStruct)(kptr)
			if k.len != key.len || b.tophash[i] != top {  <------- SEGV
				continue
			}
			if k.str == key.str || memequal(k.str, key.str, uintptr(key.len)) {
				return add(unsafe.Pointer(b), dataOffset+abi.MapBucketCount*2*goarch.PtrSize+i*uintptr(t.ValueSize)), true
			}
		}
	}

This stack sAEkLA was reported by telemetry:

• crash/crash
• runtime.throw:+9
• runtime.sigpanic:+33
• runtime.mapaccess2_faststr:+84
• golang.org/x/tools/internal/imports.(*DirInfoCache).Load:+3
• golang.org/x/tools/internal/imports.ScanModuleCache.func3:+6
• golang.org/x/tools/internal/gopathwalk.(*walker).shouldSkipDir:+8
• golang.org/x/tools/internal/gopathwalk.(*walker).walk:+68
• golang.org/x/tools/internal/gopathwalk.(*walker).walk:+121
• golang.org/x/tools/internal/gopathwalk.(*walker).walk.func1:+5
• runtime.goexit:+0

golang.org/x/tools/[email protected] go1.23.8 linux/amd64 vscode (1)

[gabyhelp]

Related Issues

• x/tools/gopls: panic in aeshashbody on behalf of mapaccess2_faststr: string memory corrupted #71367
• runtime: SEGV in mapaccess2 (go1.23.2 darwin/amd64) #71123
• x/tools/gopls: sigpanic in persistent.(*mapNode).forEach (bad SP) #71115
• x/tools/gopls: panic in internal/lsp/cache.typeCheckBatch.importMap #61512 (closed)
• x/tools/gopls: invalid memory address or nil pointer dereference on highlight #68927 (closed)
• x/tools/gopls: impossible crash in persistent.Map decref #72931
• x/tools/gopls: crash in PackageStats #40224 (closed)
• x/tools/gopls: SEGV in gcimporter.iexportCommon (bad SP) #72135
• x/tools/gopls: panic during internal/cache.(*analysisNode).typeCheck (crash) #67595 (closed)
• x/tools/gopls: Highlight: nil deref panic on CompositeLiteral with no type #68918 (closed)

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