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Fix theoretical lockfile data race. #1087

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merged 2 commits into from
Feb 7, 2025
Merged

Fix theoretical lockfile data race. #1087

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af5d278
Fix theoretical lockfile data race.
azteca1998 Feb 6, 2025
5ec4787
Merge branch 'main' into fix-theoretical-lockfile-race
azteca1998 Feb 6, 2025
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24 changes: 12 additions & 12 deletions src/executor/contract.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -256,9 +256,13 @@ impl AotContractExecutor {
})
.collect::<Result<BTreeMap<_, _>>>()?;

// Build the shared library.
// Build the shared library into a temporary path.
let temp_path = NamedTempFile::new()?
.into_temp_path()
.keep()
.to_native_assert_error("can only fail on windows")?;
let object_data = crate::module_to_object(&module, opt_level)?;
crate::object_to_shared_lib(&object_data, &output_path)?;
crate::object_to_shared_lib(&object_data, &temp_path)?;

// Write the contract info.
fs::write(
Expand All @@ -269,6 +273,10 @@ impl AotContractExecutor {
})?,
)?;

// Atomically move the built shared library to the correct path. This will avoid data races
// when loading contracts.
fs::rename(temp_path, &output_path)?;

drop(lock_file);
Self::from_path(output_path)
}
Expand All @@ -280,10 +288,9 @@ impl AotContractExecutor {
/// again.
pub fn from_path(path: impl Into<PathBuf>) -> Result<Option<Self>> {
let path = path.into();
if LockFile::exists(&path)? {
return Ok(None);
}

// Note: Library should load first, otherwise there could theoretically be a race condition.
// See the `new_into` function's code for details.
let library = Arc::new(unsafe { Library::new(&path)? });
let contract_info =
serde_json::from_str(&fs::read_to_string(path.with_extension("json"))?)?;
Expand Down Expand Up @@ -630,13 +637,6 @@ impl LockFile {
Err(e) => Err(e),
}
}

pub fn exists(path: impl Into<PathBuf>) -> io::Result<bool> {
let path: PathBuf = path.into();
let path = path.with_extension("lock");

fs::exists(path)
}
}

impl Drop for LockFile {
Expand Down
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