thodg/libgit2/src

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  • Hash : 0933fdc5
    Author : Patrick Steinhardt
    Date : 2018-05-04T13:40:54

    global: adjust init count under lock Our global initialization functions `git_libgit2_init()` and `git_libgit2_shutdown()` both adjust a global init counter to determine whether we are the first respectively last user of libgit2. On Unix-systems do not do so under lock, though, which opens the possibility of a race between these two functions: Thread 1 Thread 2 git__n_inits = 0; git_libgit2_init(); git_atomic_inc(&git__n_inits); /* git__n_inits == 1 */ git_libgit2_shutdown(); if (git_atomic_dec(&git__n_inits) != 0) /* git__n_inits == 0, no early exit here */ pthread_mutex_lock(&_init_mutex); shutdown_common(); pthread_mutex_unlock(&_init_mutex); pthread_mutex_lock(&_init_mutex); init_once(); pthread_mutex_unlock(&_init_mutex); So we can end up in a situation where we try to shutdown shared data structures before they have been initialized. Fix the race by always locking `_init_mutex` before incrementing or decrementing `git__n_inits`.

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