LSP crashes with SIGSEGV when processing service definitions (protocompile v0.14.2)

[Okxdd123]

Buf LSP Server Crashes with SIGSEGV when Processing Service Definitions

Environment

• Buf Version: 1.61.0
• OS: macOS 26.2 (Build 25C5048a)
• VS Code Version: 1.106.2
• Architecture: arm64
• protocompile Version: v0.14.2-0.20251120233202-3f9009bcd6c8

Description

The Buf LSP server crashes with a segmentation fault (SIGSEGV) when opening a .proto file containing a service definition. The crash occurs consistently and prevents the LSP from functioning.

Error Message

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x1016ed1fc]

goroutine 49 [running]:
github.com/bufbuild/protocompile/experimental/ir.MessageValue.Field({{{0x0?}, 0x0?, 0x55419a?}}, {{{0x0?}, 0x0?, 0x0?}})
    github.com/bufbuild/protocompile@v0.14.2-0.20251120233202-3f9009bcd6c8/experimental/ir/ir_value.go:793 +0xcc
github.com/bufbuild/protocompile/experimental/ir.Service.Deprecated({{{0x14002d09b08?}, 0x140031a7188?, 0x1aa?}})
    github.com/bufbuild/protocompile@v0.14.2-0.20251120233202-3f9009bcd6c8/experimental/ir/ir_service.go:111 +0x7c
github.com/bufbuild/protocompile/experimental/ir.Symbol.Deprecated({{{0x14002d09b08?}, 0x14002fa28d0?, 0x1b7b380?}})
    github.com/bufbuild/protocompile@v0.14.2-0.20251120233202-3f9009bcd6c8/experimental/ir/ir_symbol.go:144 +0xc4
github.com/bufbuild/buf/private/buf/buflsp.(*symbol).GetSymbolInformation(0x14004e6c900)
    github.com/bufbuild/buf/private/buf/buflsp/symbol.go:297 +0x148
github.com/bufbuild/buf/private/buf/buflsp.(*server).DocumentSymbol.(*file).GetSymbols.func1(...)
    github.com/bufbuild/buf/private/buf/buflsp/file.go:991
github.com/bufbuild/buf/private/buf/buflsp.(*server).DocumentSymbol(0x1400006ae40?, {0x101cb2960?, 0x140052e6aa0?}, 0x1016a3db4?)
    github.com/bufbuild/buf/private/buf/buflsp/server.go:553 +0x138

Root Cause

The crash occurs in ir.Service.Deprecated() when it attempts to access the deprecated option of a service through MessageValue.Field(). The issue is that the MessageValue is nil, but the code doesn't perform a nil check before dereferencing.

The crash happens during the DocumentSymbol request, specifically when the LSP tries to extract symbol information including the deprecated status.

Steps to Reproduce

1. Create a .proto file with the following content:

syntax = "proto3";

package api.mb_tenant_news.v1.timeline;

import "google/protobuf/timestamp.proto";
import "buf/validate/validate.proto";

option go_package = "example.com/api/timeline;timeline";

// Timeline service
service Timeline {
  rpc ListTimeline(ListTimelineRequest) returns (ListTimelineResponse);
}

message ListTimelineRequest {
  string title = 1;
}

message ListTimelineResponse {
  repeated string items = 1;
}

2. Open the file in VS Code with Buf LSP enabled
3. The LSP crashes immediately with SIGSEGV

Expected Behavior

The LSP should handle services without explicit deprecated options gracefully and not crash.

Actual Behavior

The LSP crashes with a nil pointer dereference when trying to access the service's options.

Workarounds Attempted

1. ✅ Adding option deprecated = false; to the service - Still crashes
2. ✅ Setting BUF_BETA_SUPPRESS_WARNINGS=1 - Still crashes
3. ✅ Disabling Buf LSP - Works but loses LSP functionality

Analysis

Looking at the stack trace:

• ir_service.go:111 calls Service.Deprecated()
• This internally calls MessageValue.Field() at ir_value.go:793
• The MessageValue is nil, causing the panic

The code should either:

1. Check if the MessageValue is nil before calling .Field()
2. Return a default value (false) when options are not present
3. Properly initialize the MessageValue for services without options

Minimal Reproducible Example

I can provide the complete proto files if needed. The issue occurs with any service definition, regardless of whether it has options or not.

Additional Context

• The proto files are syntactically correct and compile successfully with protoc
• The issue appeared after updating to buf v1.61.0
• This affects all proto files with service definitions in our workspace
• The LSP crashes 5 times in 3 minutes and then stops restarting

Proposed Fix

In github.com/bufbuild/protocompile/experimental/ir/ir_service.go:111, the Deprecated() method should check if the service options MessageValue is nil before attempting to access fields:

func (s Service) Deprecated() bool {
    opts := s.Options()
    if opts.IsZero() {  // Add nil/zero check
        return false
    }
    // ... existing code
}

---

Impact: This bug prevents the LSP from working entirely, breaking developer productivity for anyone using service definitions in their proto files.

[doriable]

So I took a look into this issue, and was unable to reproduce the behaviour with the instructions provided.

I appreciate the details provided in the issue and I have a quick note/question that might help with the investigation:

The root cause claimed here is that we need to do a nil check in protocompile, however, under "Workaround Attempted":

✅ Adding option deprecated = false; to the service - Still crashes

This would make it so that the options would no longer be empty for the service definition, and yet the crashing persists. To me, this indicates that the offending proto source is not the service definition that had the option added.

It is worth noting that *ir.File.Symbols() in protocompile includes symbols imported by the file also.

When you see the crashing behaviour, are there any imports that you may be using that might have service definitions that are triggering this crash? My goal is to get a repro going on my end so I can help put out a fix for this.

[Okxdd123]

I finally found the problem. It was caused by my local dependency on the third_party/google/protobuf/descriptor.proto file. I updated the entire google/protobuf directory to Protocol Buffers v33.1 for my local files, and successfully resolved the issue.

Thank you for your concern about this problem.