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hiroTamada
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Jan 29, 2026
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| case w.resizeChan <- &guest.WindowSize{Rows: resizeMsg.Resize.Rows, Cols: resizeMsg.Resize.Cols}: | ||
| default: | ||
| // Channel full, skip | ||
| } |
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Panic risk when sending to closed resize channel
Medium Severity
The resizeChan is closed via defer (line 129) before the WebSocket is closed (line 75), due to LIFO defer ordering. The wsReadWriter.Read method's select statement at lines 228-232 sends to w.resizeChan, but sending to a closed channel in Go causes a panic—even within a select with a default case. If a resize message arrives after ExecIntoInstance returns but before ExecHandler completes, the orphaned stdin goroutine could panic when processing that message.
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Fixes some terminal behavior:
terminal-behavior.mov
Note
Medium Risk
Touches the exec streaming path across API, gRPC client, and guest-agent, including concurrency around shared gRPC streams and protocol changes; regressions could break interactive shells or exec I/O.
Overview
Adds end-to-end terminal resize support for interactive
execsessions: the API now accepts initialrows/colsin the first WebSocket message and parses subsequent{"resize":{...}}control messages, forwarding them to the guest over gRPC.Updates the guest protocol (
guest.proto+ regeneratedguest.pb.go) and client/agent implementations to carry window dimensions (ExecStart.rows/colsandExecRequest.resize), apply them viapty.StartWithSize/pty.Setsize, and guard concurrent gRPC stream sends.Build tooling is adjusted to pin/install
protoc-gen-go/protoc-gen-go-grpcviatools.go/go.modand a newmake install-proto-toolsstep; adds a unit test covering TTY env defaults/overrides in the guest agent.Written by Cursor Bugbot for commit 6283407. This will update automatically on new commits. Configure here.