[gnutls-devel] GnuTLS | Use custom allocators for GMP to make sure temporary secrets (41c9c845)

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Luke D'Alessandro started a new discussion on lib/nettle/init.c: https://gitlab.com/gnutls/gnutls/-/commit/41c9c845a342359327403431050d3458246896af#note_1071304858

> +
> +	/* Check if non-default allocators are being used.
> +	 * Some applications like guile override GMP allocators
> +	 * with GC capable alternatives. Do nothing if this is
> +	 * the case.
> +	 */
> +	mp_get_memory_functions(&allocfunc, &reallocfunc, &freefunc);
> +	mp_set_memory_functions(NULL, NULL, NULL);
> +	mp_get_memory_functions(&defallocfunc, &defreallocfunc, &deffreefunc);
> +	if (reallocfunc != defreallocfunc || freefunc != deffreefunc) {
> +		mp_set_memory_functions(allocfunc, reallocfunc, freefunc);
> +		return (0);
> +	}
> +
> +	/* Overload GMP allocators with safe alternatives */
> +	mp_set_memory_functions(NULL, gnutls_realloc_zero, gnutls_free_zero);

This causes a segfault during `__run_exit_handlers` if `libgnutls.so` is unloaded before GMP tries to free memory. See issue 1398. I think gnutls needs to at least store the previous functions and restore them as part of `gnutls_crypto_deinit()`. Assuming this gets called prior to `exit()` it will avoid the issue.

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