fix: make lock acquisition signal-safe

install.sh

@@ -86,6 +86,11 @@ cleanup() {
   [ -z "$WORK_DIR" ] || rm -rf "$WORK_DIR"
 }
 
+enable_signal_traps() {
+  trap 'exit 130' INT
+  trap 'exit 143' TERM
+}
+
 require_https() {
   # Args: <url> <label>
   case "$1" in https://*) return 0 ;; esac
@@ -221,14 +226,26 @@ prepare_destination() {
   mkdir -p "$FINAL_PARENT"
 
   waited=0
-  until mkdir "$lock_dir" 2>/dev/null; do
+  while :; do
+    pending_signal_status=0
+    trap 'pending_signal_status=130' INT
+    trap 'pending_signal_status=143' TERM
+
+    # Defer cancellation until ownership is known. The subshell prevents a
+    # process-group signal from killing mkdir after it creates the lock.
+    if (trap '' INT TERM; CLOUDSMITH_CLI_LOCK_OWNER_PID=$$ mkdir "$lock_dir") 2>/dev/null; then
+      LOCK_DIR="$lock_dir"
+      enable_signal_traps
+      [ "$pending_signal_status" -eq 0 ] || exit "$pending_signal_status"
+      break
+    fi
+    enable_signal_traps
+    [ "$pending_signal_status" -eq 0 ] || exit "$pending_signal_status"
+
     [ "$waited" -lt 120 ] || die "timed out waiting for installation lock: $lock_dir"
     sleep 1
     waited=$((waited + 1))
   done
-  # Track the lock for cleanup only once this process owns it, so a waiter
-  # that dies never releases another installer's lock.
-  LOCK_DIR="$lock_dir"
 }
 
 reuse_existing_install() {
@@ -373,8 +390,7 @@ main() {
 }
 
 trap cleanup EXIT
-trap 'exit 130' INT
-trap 'exit 143' TERM
+enable_signal_traps
 
 parse_args "$@"
 set_default_install_root

tests/install.bats

@@ -627,6 +627,47 @@ executable=$bin_dir/cloudsmith"
   [ -d "$final_parent/.install.lock" ]
 }
 
+@test "a signal during lock acquisition exits without leaving a stale lock" {
+  build_fixture "$FIXTURE_DIR" "1.19.0" "$TEST_TARGET"
+  local final_parent="$INSTALL_ROOT/1.19.0/$TEST_TARGET"
+  local shim_dir="$BATS_TEST_TMPDIR/signal-mkdir"
+  local signal_marker="$BATS_TEST_TMPDIR/mkdir-sent-signal"
+  mkdir -p "$shim_dir"
+
+  cat > "$shim_dir/mkdir" <<'EOF'
+#!/usr/bin/env bash
+"$REAL_MKDIR" "$@"
+status=$?
+last_arg=
+for arg do last_arg="$arg"; done
+if [ "$status" -eq 0 ]; then
+  case "$last_arg" in
+    */.install.lock)
+      : > "$MKDIR_SIGNAL_MARKER"
+      kill -TERM "$CLOUDSMITH_CLI_LOCK_OWNER_PID"
+      ;;
+  esac
+fi
+exit "$status"
+EOF
+  chmod +x "$shim_dir/mkdir"
+
+  run --separate-stderr env \
+    PATH="$shim_dir:$PATH" \
+    REAL_MKDIR="$(command -v mkdir)" \
+    MKDIR_SIGNAL_MARKER="$signal_marker" \
+    "$INSTALL_SH" \
+    --version 1.19.0 \
+    --target "$TEST_TARGET" \
+    --install-root "$INSTALL_ROOT" \
+    --manifest-url "$FIXTURE_URL/manifest.txt"
+
+  [ "$status" -eq 143 ]
+  [ -f "$signal_marker" ]
+  [ ! -e "$final_parent/.install.lock" ]
+  [ ! -e "$final_parent/cloudsmith/cloudsmith" ]
+}
+
 @test "concurrent installs of the same version both succeed" {
   build_fixture "$FIXTURE_DIR" "1.19.0" "$TEST_TARGET"