New submission from George King <[email protected]>:
I was browsing the Blake2b module implementation in master and noticed two
subtle issues in blake2b_impl.c. There are two places where the GIL gets
released; both of them appear flawed.
py_blake2b_new_impl, line 221. The ALLOW_THREADS block fails to acquire/release
self->lock.
_blake2_blake2b_update, line 279. The lock is lazily allocated correctly on
line 279. However the test on 282 that chooses to release the GIL or not fails
to take into account the length test. This means that once a large block is fed
to `update`, then every call to update will release the GIL, even if it is a
single byte.
It should look something more like this:
```
bool should_allow_threads = (buf.len >= HASHLIB_GIL_MINSIZE);
if (should_allow_threads && self->lock == NULL)
self->lock = PyThread_allocate_lock();
if (should_allow_threads && self->lock != NULL) { ... }
else { ... }
```
This respects the size criterion, and also protects against the case where the
lock allocation fails.
----------
components: Extension Modules
messages: 339394
nosy: gwk
priority: normal
severity: normal
status: open
title: Blake2b/s implementations have minor GIL issues
versions: Python 3.7
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Python tracker <[email protected]>
<https://bugs.python.org/issue36519>
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