# Rust Concurrency
# Detects lock guards obtained via lock().await and additional await in same block.
id: rust-lock-held-across-await
name: Lock Held Across Await
severity: error
category: concurrency
defect_class: async-misuse
inline_tier: blocking
language: rust

message: "Lock guard may be held across await — release lock before awaiting other work"

description: |
  Awaiting while holding a mutex guard can cause contention and deadlocks.

  ✅ FIX: limit lock scope, clone needed data, then await outside lock lifetime.

query: |
  (block
    (let_declaration
      pattern: (identifier) @GUARD
      value: (await_expression
        (call_expression
          function: (field_expression
            value: (_)
            field: (field_identifier) @LOCKFN))))
    (_)*
    (expression_statement (await_expression) @LATER_AWAIT)
    (#eq? @LOCKFN "lock"))

metavars:
  - GUARD
  - LOCKFN
  - LATER_AWAIT

cwe:
  - CWE-833
owasp:
  - A09
confidence: low

has_fix: false

tags:
  - rust
  - concurrency
  - mutex
  - async

examples:
  bad: |
    let guard = state.lock().await;
    do_network().await;

  good: |
    {
        let guard = state.lock().await;
        update(&guard);
    }
    do_network().await;