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Date: Sun, 25 Oct 2020 23:29:43 -0400
From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Message-ID: <20201026032943.GK534@brightrain.aerifal.cx>
References: <20201026005028.GI534@brightrain.aerifal.cx>
 <20201026005912.GJ534@brightrain.aerifal.cx>
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In-Reply-To: <20201026005912.GJ534@brightrain.aerifal.cx>
User-Agent: Mutt/1.5.21 (2010-09-15)
Subject: Re: [musl] Status report and MT fork

On Sun, Oct 25, 2020 at 08:59:20PM -0400, Rich Felker wrote:
> diff --git a/ldso/dynlink.c b/ldso/dynlink.c
> index af983692..32e88508 100644
> --- a/ldso/dynlink.c
> +++ b/ldso/dynlink.c
> @@ -21,6 +21,7 @@
>  #include <semaphore.h>
>  #include <sys/membarrier.h>
>  #include "pthread_impl.h"
> +#include "fork_impl.h"
>  #include "libc.h"
>  #include "dynlink.h"
>  
> @@ -1404,6 +1405,17 @@ void __libc_exit_fini()
>  	}
>  }
>  
> +void __ldso_atfork(int who)
> +{
> +	if (who<0) {
> +		pthread_rwlock_wrlock(&lock);
> +		pthread_mutex_lock(&init_fini_lock);
> +	} else {
> +		pthread_mutex_unlock(&init_fini_lock);
> +		pthread_rwlock_unlock(&lock);
> +	}
> +}
> +
>  static struct dso **queue_ctors(struct dso *dso)
>  {
>  	size_t cnt, qpos, spos, i;
> @@ -1462,6 +1474,12 @@ static struct dso **queue_ctors(struct dso *dso)
>  	}
>  	queue[qpos] = 0;
>  	for (i=0; i<qpos; i++) queue[i]->mark = 0;
> +	for (i=0; i<qpos; i++) if (queue[i]->ctor_visitor->tid < 0) {
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Invalid access as-is, should be queue[i]->ctor_visitor && ...

> +		error("State of %s is inconsistent due to multithreaded fork\n",
> +			queue[i]->name);
> +		free(queue);
> +		if (runtime) longjmp(*rtld_fail, 1);
> +	}
>  
>  	return queue;
>  }

Rich